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The impact of frequent napping and nap practice on sleep-dependent memory in humans

Elizabeth a. mcdevitt.

1 Department of Psychology, University of California, Riverside, Riverside, CA 92521 USA

2 Princeton Neuroscience Institute, Princeton University Princeton, NJ, 08544 USA

Negin Sattari

3 Department of Cognitive Sciences, University of California, Irvine Irvine, CA, 92697 USA

Katherine A. Duggan

4 Department of Psychiatry, University of Pittsburgh School of Medicine Pittsburgh, PA, 15261 USA

Nicola Cellini

5 Department of General Psychology, University of Padova Via Venezia 8, Padova, CA, 315131 Italy

Lauren N. Whitehurst

Chalani perera, nicholas reihanabad, samantha granados, lexus hernandez, sara c. mednick, associated data.

The data analyzed in this study are included as Supplementary Information. All other study materials are available upon request to the authors.

Napping benefits long-term memory formation and is a tool many individuals use to improve daytime functioning. Despite its potential advantages, approximately 47% of people in the United States eschew napping. The goal of this study was to determine whether people who endorse napping at least once a week (nap+) show differences in nap outcomes, including nap-dependent memory consolidation, compared with people who rarely or never nap (nap−). Additionally, we tested whether four weeks of nap practice or restriction would change sleep and performance profiles. Using a perceptual learning task, we found that napping enhanced performance to a greater degree in nap+ compared with nap− individuals (at baseline). Additionally, performance change was associated with different electrophysiological sleep features in each group. In the nap+ group, spindle density was positively correlated with performance improvement, an effect specific to spindles in the hemisphere contralateral to the trained visual field. In the nap− group, slow oscillatory power (0.5–1 Hz) was correlated with performance. Surprisingly, no changes to performance or brain activity during sleep emerged after four weeks of nap practice or restriction. These results suggest that individual differences may impact the potential benefits of napping on performance and the ability to become a better napper.

Introduction

Sleep plays an important role in stabilizing or enhancing memory for newly learned information (i.e., memory consolidation) 1 . Daytime naps are sometimes as effective as nocturnal sleep in facilitating these memory processes 2 – 4 . Performance enhancement effects from naps have been found across a wide range of cognitive abilities, including episodic memory 5 , 6 , emotion regulation 7 , 8 , procedural skills 9 , and attention 10 . Napping has also been endorsed as a way to boost creativity 11 , 12 and productivity 13 , improve performance in athletes 14 , and help people cope with fatigue-related to shiftwork 15 – 17 .

Despite the demonstrated benefits of napping, not everyone naps. In the United States, the National Sleep Foundation Sleep Health Index 2014 18 reported that 53% of adults nap regularly, defined as having napped at least once in the past 7 days. Though there is no consensus for what defines a “napper” or “non-napper”, napping behavior in a young, healthy population likely follows different regulatory patterns and environmental opportunities than other populations that report frequent napping, e.g., infants, preschool children, older adults, and sleep-disordered individuals 19 – 24 . In young, healthy adults, consistent patterns in subjective reports and objective measures (e.g., sleep electroencephalography (EEG)) have emerged suggesting that there may in fact be differences between people who endorse napping and people who do not 25 . Non-nappers often report that they eschew the practice because they wake up feeling groggy, unproductive, and do not receive any benefits from a nap 26 . At the physiological level, this post-waking cognitive impairment (i.e., sleep inertia) may be associated with the amount of slow wave sleep (SWS) and waking from SWS 27 . Indeed, we previously found that non-nappers spend more time in deep SWS, whereas frequent napping was associated with more time in light, Stage 1 and Stage 2 sleep during a daytime nap 28 . Thus, day-to-day experiences with napping may change the quality of daytime sleep, which may, in turn, impact memory processing during the nap and symptoms of sleep inertia upon awakening.

Here, we investigated the impact of prior napping (nap+ vs. nap−) on nap-dependent memory consolidation and sleep inertia. Additionally, we used a cross-over design to test if four weeks of “nap practice” (at least 3 naps/week) or “nap restriction” in nap+ and nap− individuals would alter sleep physiology and performance profiles. Participants took an in-lab polysomnographically-recorded (PSG) nap at three different time points during the study – baseline, mid-intervention and post-intervention. On each in-lab nap day, pre- and post-nap behavioral performance was measured using a perceptual learning task (texture discrimination) that has shown the same magnitude of sleep-dependent memory benefit from a nap as a full night of sleep 2 . We also tested post-nap cognitive functioning using a descending subtraction test 29 , 30 , and collected ratings of subjective sleepiness throughout the day.

We first aimed to replicate the finding 2 that same-day performance on a texture discrimination task only shows improvement following a nap by comparing individuals who napped (ignoring prior nap experience as in the original study) with individuals who remained awake. Critically, the nap group was comprised of both nap+ and nap− individuals. We hypothesized that by taking this difference in napping experience into account, we would see different performance outcomes between nap+ and nap− following a nap, including greater perceptual learning gains, less sleep inertia (as indexed by descending subtraction test performance) and less subjective sleepiness in nap+ individuals 4. To summarize, we hypothesized that nap+ participants would do better and feel better following a nap than nap− participants.

Our second aim was to examine how individual differences in sleep EEG features were associated with performance outcomes, namely minutes and percent of each sleep stage, sleep spindles, slow oscillation (0.5–1 Hz), delta (1–4 Hz) and sigma (12–15 Hz) power during non-rapid eye movement (NREM) sleep, and theta (4–8 Hz) power during rapid eye movement (REM) sleep. Prior work suggests that multiple consolidation processes, not necessarily mutually exclusive, may underlie perceptual learning. Each of these proposed processes tends to be linked to different sleep features, e.g., synaptic homeostasis and slow wave activity 31 , recovery from perceptual deterioration and SWS 2 , reactivation during NREM sleep 32 and sleep spindle activity 33 (i.e., active systems consolidation hypothesis) 1 , synaptic strengthening that leads to improvement above and beyond the performance level achieved during training, which may depend on a combination of NREM and REM sleep 2 , 34 – 37 . Given the overall complexity of this picture, we did not think that group level differences (e.g., increased SWS in nap−) would sufficiently explain why one group might receive more perceptual learning benefits from a nap. Rather, we hypothesized that prior nap experience would moderate the associations between sleep features and performance outcomes. Specifically, because we thought nap+ individuals would show more nap-related performance improvement, we expected that sleep EEG features linked to task improvement (spindles and REM sleep) would be more strongly associated with performance changes in the nap+ compared with the nap− group.

Finally, we aimed to test if nap-related learning benefits are experience-dependent. We hypothesized that napping is a trainable skill, such that nap− individuals who practiced napping for four weeks would show more perceptual learning gains, less sleep inertia and less subjective sleepiness following a daytime nap.

Visit 1: Does prior napping affect post-nap performance, sleep brain activity, and sleep inertia?

Perceptual learning: nap vs. wake.

Participants completed a texture discrimination task (TDT) two times on the same day, once in the morning and once in the evening, while either remaining awake or taking a nap between task sessions. We computed the difference in thresholds between sessions, and replicated the classic finding 2 that a nap enhances TDT performance compared to wake [ t (67) = 1.95, p  = 0.056, Cohen’s d  = 0.49, independent samples t -test]. Discrimination thresholds significantly improved in participants who napped [ t (47) = 2.69, p  = 0.01, one-sample t -test] and were not different from zero in participants who remained awake [ t (20) = −0.58, p  = 0.57, one-sample t -test] (Fig.  1b ). Change in performance was positively correlated with SWS min ( r  = 0.36, p  = 0.01) and SWS% ( r  = 0.32, p  = 0.03), as well as the product of SWS and REM min (SWSxREM, r  = 0.34, p  = 0.02). The latter result is consistent with the classic studies we aimed to replicate here 2 , 36 , although we note this may not be the best way to statistically test the combined contribution of SWS and REM to performance improvement 37 . Also, learning was negatively correlated with Stage 2% ( r  = −0.33, p  = 0.02), which may reflect a trade-off between Stage 2 and SWS (amounts of Stage 2 and SWS were inversely correlated; minutes: r  = −0.45, p  = 0.001, percent: r  = −0.69, p  < 0.001).

Visit 1 Baseline. ( a ) In-lab test day procedure. Texture discrimination task (TDT) thresholds were obtained at 9AM and 5PM. All participants napped between 1:30–3:30PM. Solid arrows indicate times of Karolinska Sleepiness Scale (KSS) administration; dashed arrows indicate times of the descending subtract test (DST) administration. ( b ) TDT threshold difference at baseline for the Wake ( n  = 21, white bar) and Nap ( n  = 48, black bar) groups. Within the Nap group, only nap+ ( n  = 26, hatched bar) showed learning; nap− ( n  = 22, solid gray bar) did not show significant improvement. All subsequent panels have the same number of independent data points ( n ) represented in each group unless noted. ( c ) Performance improvement was correlated with Stage 2 spindle density (grand average plotted), but in opposing directions for nap+ ( r  = 0.38, p  = 0.055) and nap− ( r  = −0.59, p  = 0.004). ( d ) Nap+ had more spindles ( p  = 0.04) and greater spindle density ( p  = 0.008) during Stage 2 than nap− (C3-P3 avg shown). ( e ) Correlation coefficients (Pearson r ) for correlations between performance improvement and Stage 2 sleep spindle densities (note: In the nap− group, the Left correlation is n  = 20 and Contralateral and Ipsilateral correlations are both n  = 21, due to missingness from bad electrodes). There were also differing  associations between performance and ( f ) NREM slow oscillation power (SO, 0.5–1 Hz) and ( g ) REM theta power (4–8 Hz) based on nap+/nap− grouping. For panels (e), (f) and (g), an asterisk above or below the bar indicates a significant correlation; brackets indicate significant differences in r -values between groups (note: NREM SO correlation in nap− had n  = 21; REM theta correlations had nap+ frontal n  = 15, nap+ central n  = 17, nap− frontal n  = 16, nap− central n  = 15; reduced n due to naps not containing REM sleep and/or bad electrodes). ( h ) DST performance change 5 min after awakening from the nap (note: nap+ n  = 25 and nap− n  = 20; reduced n due to experimenter error and performance that did not meet inclusion criteria). ŧ indicates p  ≤  0.07, * indicates p  <  0.05, **indicates p  <  0.005. Error bars are ± 1 SEM .

Perceptual Learning: Nap+ vs. Nap−

We re-analyzed the above data, now separating the nap group into two subgroups based on prior nap experience (nap+ and nap−). As predicted, nap+ showed significant performance gains after a nap [ t (25) = 3.38, p  = 0.002, one-sample t -test], whereas performance change in nap− did not differ from zero [ t (21) = 0.74, p  = 0.47, one-sample t -test] (Fig.  1b ), although the difference between the two groups did not reach statistical significance [ t (46) = 1.35, p  = 0.18, Cohen’s d  = 0.39, independent samples t -test). Compared with the wake group, only the nap+ group was significantly better [nap+ vs. wake: t (45) = 2.42, p  = 0.02, Cohen’s d  = 0.70, independent samples t -test; nap− vs. wake: t (41) = 0.93, p  = 0.36, Cohen’s d  = 0.28, independent samples t-test]. These effects were not due to differences in pre-nap thresholds between wake, nap+ and nap− groups [ F (2,66) = 0.79, p  = 0.46, one-way ANOVA]. Together with the above results, this analysis demonstrates that the nap-dependent improvement observed in the Nap vs. Wake analysis was driven by nap+ individuals, and suggests that not all individuals show learning benefits from daytime sleep.

Daytime Sleep Architecture

During the first in-lab visit (prior to the intervention group assignment), we found no significant differences in total sleep time or minutes or percent of any sleep stage between nap+ and nap− (all p s > 0.29) (Supplementary Table  2 ). Since daytime sleep may be directly related to nighttime sleep, we also compared the prior night’s sleep between nap+ and nap−, using actigraphy, and found no differences (Supplementary Table  3 ). Additionally, total sleep time the night before the experimental day did not correlate with nap sleep stages in either group (all p s > 0.17), or the sample as a whole (all p s > 0.14).

Differences were noted, however, in sleep spindle events during the nap. Nap+ had approximately 31% more sleep spindle events during Stage 2 sleep compared to nap− [C3-P3 avg , nap+ mean 87.6 (SD = 34.5) vs. nap− mean 66.8 (SD = 33.7) spindle events, t (46) = 2.11, p  = 0.04, Cohen’s d  = 0.61, independent samples t -test] (Fig.  1d ). Given inter-subject variability in duration of Stage 2 and SWS, we focused our remaining analyses on spindle density (spindle count/minutes). In the left hemisphere, nap+ showed greater spindle density than nap− for Stage 2 sleep [C3-P3 avg , nap+ mean 2.2 (SD = 0.4) vs. nap− mean 1.8 (SD = 0.5) spindles/min, t (46) = 2.79, p  = 0.008, Cohen’s d  = 0.80, independent samples t -test], but no differences in the right hemisphere (C4-P4 avg , p  = 0.41). Also, no differences in sleep spindles were identified during SWS in either hemisphere (all p s > 0.10).

Next, we examined spectral power in specific frequency bands of interest (NREM SO, delta, and sigma; REM theta) over frontal (F3-F4 avg ) and central (C3-C4 avg ) electrode sites. There were no differences between nap+ and nap− in any frequency band during NREM sleep, however, for REM sleep, nap+ had greater theta power [ t (30) = 2.15, p  = 0.04, Cohen’s d  = 0.77, independent samples t -test) over central sites. Together, these results indicate that nap sleep physiology was equivalent in nap+ and nap− groups across most sleep variables, with the exception of left hemisphere spindles and REM theta power. In the following section, we take a closer look at how the relation between sleep features and behavior might differ in these groups.

Brain-Behavior Relationships: Nap+ vs. Nap−

We next examined associations between sleep features and performance separately for nap+/− participants, and tested for a moderating effect of nap frequency group on these associations. Prior nap experience did not moderate the association between sleep stages and performance change, with both nap+ and nap− showing similar direction and magnitude of correlation coefficients. However, there were substantial differences between the groups in how sleep spindles were associated with performance (Fig.  1c,e ). In nap−, performance was consistently negatively correlated with spindle density (C3-C4-P3-P4 avg ) during Stage 2 ( r  = −0.59, p  = 0.004), SWS ( r  = −0.37, p  = 0.13, negative correlation, but non-significant), and NREM stages combined ( r  = −0.62, p  = 0.002). In nap+, there was a trending positive performance-spindle density relationship for Stage 2 ( r  = 0.38, p  = 0.055), and no significant relationship for SWS or NREM combined spindles (SWS: r  = −0.11, NREM: r  = 0.16; both p s > 0.45). The statistical difference between correlation coefficients in the two groups was significant for Stage 2 sleep spindles ( z  = 3.47, p  = 0.0005) and NREM combined ( z  = 2.84, p  = 0.004), indicating that nap group moderated the relation between spindles and performance change.

Given that learning on the TDT is retinotopically-specific 38 , we further examined Stage 2 spindles in the ipsilateral and contralateral hemispheres relative to the trained visual field location. Nap+ showed a pattern of results predicted by a retinotopic learning effect, with a positive correlation between performance and contralateral spindles ( r  = 0.50, p  = 0.009) and no significant relation between performance and ipsilateral spindles ( r  = −0.008, p  = 0.97). In nap−, both contralateral ( r  = −0.33, p  = 0.14) and ipsilateral ( r  = −0.60, p  = 0.004) spindles were negatively correlated with performance, although this association was only significant for ipsilateral spindles. There was significant moderation for both the contralateral ( z  = 2.84, p  = 0.004) and ipsilateral ( z  = 2.16, p  = 0.03) effects.

Interestingly, NREM SO and delta power strongly correlated in the positive direction with performance change in nap− (SO frontal: r  = 0.53, p  = 0.013; SO central: r  = 0.62, p  = 0.003; delta frontal: r  = 0.52, p  = 0.015; delta central: r  = 0.60, p  = 0.005), but not in nap+ (SO frontal: r  = −0.10, p  = 0.63; SO central: r  = 0.06, p  = 0.79; delta frontal: r  = 0.01, p  = 0.95; delta central: r  = 0.21, p  = 0.30) (Fig.  1f ). We note that the strong correlations within the nap− group were potentially driven by SO and delta power during SWS, which consistently showed larger magnitude correlation coefficients relative to Stage 2 (SO frontal: Stage 2 r  = 0.02 vs. SWS r  = 0.38; SO central: Stage 2 r  = 0.12 vs. SWS r  = 0.45; delta frontal: Stage 2 r  = −0.05 vs. SWS r  = 0.22; delta central: Stage 2 r  = 0.11 vs. SWS r  = 0.47). Correlation coefficients significantly differed between groups for NREM SO power over frontal ( z  = 2.20, p  = 0.03) and central ( z  = 2.11, p  = 0.03) sites; NREM delta power correlations did not significantly differ (frontal: p  = 0.07, central: p  = 0.10). NREM sigma power negatively correlated with performance only in nap− (frontal: r  = −0.45, p  = 0.03; central: r  = −0.38, p  = 0.08, non-significant), not in nap+ (frontal: r  = −0.01, p  = 0.96; central: r  = 0.15, p  = 0.46). However, tests for moderation were non-significant (frontal: p  = 0.10; central: p  = 0.08). REM theta power was positively correlated with performance in nap+ (frontal: r  = 0.58, p  = 0.02; central: r  = 0.41, p  = 0.10), but not in nap− (frontal: r  = −0.05, p  = 0.84; central: r  = −0.28, p  = 0.32) (Fig.  1g ), with non-significant tests for moderation (both p  = 0.07). Unlike the spindle result, we did not find retinotopically-specific differences in any of the frequency bands, which may be related to the more localized nature of spindles compared to more global oscillations that occur during sleep 39 – 42 . In summary, these results reveal differences in the underlying oscillatory circuitry associated with consolidation mechanisms during daytime sleep for nap+ and nap−. Specifically, we found that prior nap frequency significantly moderated the brain-behavior relationship between contralateral Stage 2 spindles and learning, and NREM SO power and learning.

Subjective sleepiness and sleep inertia: Nap+ vs. Nap−

Since non-nappers often report not enjoying napping 26 , and anecdotally complain of feeling groggy and unproductive after a nap, we measured subjective sleepiness and cognitive functioning after the nap. Participants rated their subjective sleepiness at three time points across the study day: 1) pre-nap, 2) 10 min post-nap, and 3) 90 min post-nap (see Fig.  1a ). Overall, subjective sleepiness decreased across the day [ F (2,82) = 16.46, p  < 0.001, partial eta 2  = 0.29, mixed ANOVA main effect], with a slight reduction in sleepiness, or boost in alertness, evident 10 min post-nap compared to pre-nap (trending at p  = 0.06, paired t -test), and an even further reduction in sleepiness approximately 90 min after waking compared to 10 min post-nap ( t (44) = 4.81, p  < 0.001, paired t -test). There was no main effect of group ( p  = 0.36, mixed ANOVA) and no timepoint x group interaction ( p  = 0.88, mixed ANOVA), indicating that both groups received similar boosts in alertness from the nap.

We probed the degree of sleep inertia experienced by participants using a descending subtraction test (DST) 29 , 30 to measure cognitive functioning at 11AM and again 5, 20 and 35 min after awakening from the nap (see Fig.  1a ). At 11AM (prior to the nap), there were no differences in speed (total number of correct responses) or accuracy (correct responses/total responses) between nap+/− (both p s > 0.55, independent samples t -test). The task proved to be sensitive to impairment in cognitive functioning upon awakening, with differences in speed across the day [ F (3,120) = 14.08, p  < 0.001, partial eta 2  = 0.26, mixed ANOVA main effect], including a significant dip in performance 5 min post-nap compared to pre-nap (post hoc p  = 0.005) and recovered performance by 20 min post-nap. Although accuracy showed the same general trend, it did not reach statistical significance [ F (3,120) = 2.45, p  = 0.07, partial eta 2  = 0.06, mixed ANOVA main effect]. Neither speed nor accuracy showed a main effect of group ( p s > 0.66) or timepoint × group interaction ( p s > 0.44). Numerically, as predicted, the nap− group showed greater decrements than the nap+ group. We conducted further exploratory analyses within each group at each timepoint. Upon awakening from the nap, nap− showed significant decrements in speed [ t (19) = 2.62, p  = 0.02, paired t -test] and accuracy [ t (19) = 2.44, p  = 0.02, paired t -test] compared to their pre-nap performance (Fig.  1h ). On the other hand, nap+ did not show significant impairment in speed [ t (24) = 1.06, p  = 0.30, paired t -test] or accuracy [ t (24) = 0.28, p  = 0.78, paired t -test] . By 20 min post-nap, DST speed increased in both groups relative to the 5-min assessment [nap−: t (20) = 3.43, p  = 0.003; nap+: t (24) = 5.07, p  < 0.001; paired t -tests]. Compared to pre-nap speed, nap+ were significantly faster ( t (24) = 2.68, p  = 0.01, paired t -test); on the other hand, nap− recovered, but did not improve, their speed ( t (19) = 1.06, p  = 0.30). By 35 min post-nap, the nap+ group maintained their improved speed relative to pre-nap [ t (22) = 2.04, p  = 0.05, paired t -test]; the nap− group showed a non-significant improvement in speed ( t (18) = 1.91, p  = 0.07, paired t -test). Accuracy did not show any significant differences at 20 min or 35 min post-nap compared to pre-nap in either group (all p s > 0.11). Overall these results suggest no sign of significant sleep inertia in nap+ participants, based on both subjective reports (KSS ratings) and objective performance (DST) measures. On the other hand, nap− participants, notwithstanding a similar perceived level of sleepiness as nap+, showed impaired cognitive functioning on the DST task, suggesting nap− individuals experience more performance-related sleep inertia upon awakening from a nap. However, it should be noted that these were post-hoc exploratory analyses following a non-significant omnibus test, and these results should be interpreted with caution.

Does nap Practice/Restriction change performance profiles associated with napping?

Next, we investigated the effect of four weeks of nap Practice or Restriction. Participants in the Practice condition took 3.13 (SD = 0.90) naps per week on average. Weekly nighttime sleep descriptive statistics (from actigraphy) are provided in Supplementary Table  4 . Statistics reported below are from 3 (visits 1/2/3) × 2 (nap+/nap−) × 2 (practice/restriction) mixed-model ANOVAs.

Behavioral performance

For perceptual learning, in contrast with our prediction, there was no main effect of visit or intervention (practice/restriction) and no significant interactions, indicating that neither nap practice nor restriction altered performance across time. There was, however, a main effect of nap frequency group [ F (1,36) = 5.61, p  = 0.02, partial eta 2  = 0.14, mixed ANOVA], which revealed that nap+ always showed more performance gains with a nap than nap− collapsing across visits [although note that, similar to Visit 1, the difference between groups at each visit did not reach traditional statistical significance levels, but showed a medium strength effect size [Visit 2: t (38) = 1.83, p  = 0.074, Cohen’s d  = 0.58, independent samples t -test; Visit 3: t (38) = 1.83, p  = 0.075, Cohen’s d  = 0.58, independent samples t -test] (Fig.  2a ). In other words, the differential performance outcomes observed at Visit 1 (baseline) were maintained throughout the study (Fig.  2b ). On each visit, pre-nap thresholds were comparable between nap+ and nap− (all p s > 0.20).

Nap practice/restriction intervention. ( a ) TDT threshold difference at Visit 2 and Visit 3. Nap+ ( n  = 20) always showed improvement and nap− ( n  = 20) did not. ( b ) Individual participant performance on the TDT is plotted across visits within nap frequency groups. It is visually apparent that the magnitude of nap-dependent memory improvement remains stable across the four-week nap Practice (gray lines) or nap Restriction (dotted black lines) intervention in both nap+ and nap− groups (nap+ Practice n  = 11, nap+ Restriction n  = 9, nap− Practice n  = 10, nap− Restriction n  = 10). ŧ indicates p  ≤  0.07 . Error bars are ± 1 SEM .

Daytime sleep architecture

We found no differences in nap total sleep time ( p  = 0.88), Stage 1 ( p  = 0.49), Stage 2 ( p  = 0.88), SWS ( p  = 0.57), or REM ( p  = 0.67) (reported p -values are from the 3 × 2 × 2 interaction) minutes across the intervention (Supplementary Table  5 ). Likewise, there were no changes in spindle densities (Stage 2 C3-C4-P3-P4 avg, p  = 0.30) or power spectra (NREM SO: p  = 0.64, NREM delta: p  = 0.76, REM theta: p  = 0.89) as a function of nap practice/restriction. These results indicate that short-term changes to nap frequency did not have a significant impact on the architecture of daytime sleep.

Subjective sleepiness and sleep inertia

Across the four weeks, there were no changes in subjective sleepiness after waking from the nap as a function of nap practice or restriction ( p  = 0.56). The degree of post-nap sleep inertia as measured by the DST remained stable across visits, with no changes due to nap practice or restriction (Δspeed: p  = 0.57; Δaccuracy: p  = 0.19).

This young, healthy sample of self-reported nappers (nap+) demonstrated perceptual learning with a nap, whereas self-reported non-nappers (nap−) showed no performance improvement with a nap. Importantly, when these two subgroups were combined in the same analysis (Nap vs. Wake), it appeared as though, compared with a wake control group, a nap benefited perceptual learning on this task, replicating prior work 2 , 43 . However, further analysis revealed that this result was driven by the nap+ individuals, masking the fact that not all naps are equal. Further, performance in the two groups was associated with different oscillatory features during sleep, exhibiting contrasting associations between behavioral performance and spindle density, as well as behavioral performance and SO power. Finally, four weeks of experimental nap restriction or practice was not sufficient to alter the performance profiles of either group, such that neither restricting naps in nap+ individuals decreased the cognitive benefits they derived from naps, nor did increasing naps in nap-participants boost nap-related perceptual learning. These findings suggest that nap preferences either require a longer period of training to produce measurable enhancement, or that nap preferences are not experience-dependent. These results may have far-reaching implications for a wide range of people, including sleep researchers, as well as administrators, educators, policy makers, and clinicians who may recommend occupational napping.

Although there is no agreed upon definition for habitual napping, prior studies have found that the sleep architecture in people who nap more frequently is predominated by light sleep stages, whereas infrequent napping is associated with naps containing more SWS 25 , 44 . We previously reported a dose-dependent effect of napping on nap sleep architecture—more napping during a one-week period was associated with greater amounts of Stage 1 and 2, and less SWS 28 . In the current study, we did not find macroarchitecture sleep stage differences, perhaps due to a smaller range of prior nap frequency in this sample compared to McDevitt et al . 28 . However, we did find that nap+ participants had increased Stage 2 sleep spindles, and spindle density was associated with better performance in the nap+ group only. This correlation was especially strong for spindles occurring in the hemisphere contralateral to the trained target location. While this result may potentially reflect spindle activity localized to the brain area involved in learning 33 , 45 , it is important to consider the limited spatial resolution of scalp EEG and the limited number of electrodes used in this study. Nonetheless, this is a promising result that suggests future research should pursue investigating the role of sleep spindles for visual perceptual learning.

What might be the role of spindles for this type of learning? Spindle activity has been correlated with better performance on a wide range of memory tasks 46 , 47 , including studies in which prior nap preference is unspecified 4 , 48 – 51 or primarily tested regular nappers 24 , 44 . Spindles are thought to reflect replay or reactivation of newly learned information, leading to transfer of information between brain networks and strengthening or modification of synaptic connections (active systems consolidation model) 46 . In the perceptual learning domain, increased power in the sigma band (i.e., spindle frequency) has previously been associated with performance improvement in humans 33 . Following perceptual learning in rodents, spindle oscillations were critical for relaying information between the thalamus (lateral geniculate nucleus) and primary visual cortex, ultimately leading to sleep-dependent response changes in V1 52 . Thus, spindles may be an electrophysiological marker of a consolidation process that reactivates information and strengthens synaptic connections in the perceptual learning network, leading to improved behavioral performance. It is possible that this reweighting could be occurring in low-level visual areas, at higher-level decision-making units, or both 53 – 55 .

The positive spindle correlation in nap+ individuals and significant moderation was specific to Stage 2 sleep. Studies tend to differ in whether they report memory associations with Stage 2 spindles 48 , 49 , 56 , 57 , SWS spindles 51 , or spindles in NREM sleep combined 4 , 50 , 58 , 59 . Prior work in the perceptual learning domain found that spindle activity during Stage 2 sleep, but not SWS, played a critical role 33 . Why might Stage 2 spindles, rather than SWS spindles, be more strongly related to the sleep-based consolidation examined in this study? A model by Genzel and colleagues 39 proposes that light NREM sleep (i.e., Stage 2) may favor global information exchange and active potentiation, whereas SWS promotes local weakening of synaptic units (synaptic homeostasis, to be discussed further below). In their model, spindles do not drive the global replay event (cf. 60 ). Rather, spindles immediately follow these replay events and trigger local synaptic plasticity in cortical networks involved in the preceding replay event. Extending their model to the current results, we posit that Stage 2 may favor consolidation of visual perceptual learning by facilitating global thalamocortical communication (e.g., replay between thalamus and visual cortex) 52 and plasticity in cortical synapses (e.g., long-term potentiation in visual cortex) 61 .

It is also likely that there are other consolidation mechanisms at work during sleep 39 . For example, prior studies have shown that repeated training on the texture discrimination task without sleep typically leads to perceptual deterioration; and while a nap with NREM sleep can reverse the deterioration, REM sleep is required for performance improvement above baseline 43 , 62 – 65 . Notably, in the current study, post-nap performance in nap− participants did not significantly deteriorate between sessions, and nap− performance was correlated with power in slow frequency bands, which has been demonstrated to be critical for perceptual learning 31 . This suggests that even if nap− individuals did not have spindle-related performance gains, they may have still benefitted from slow wave-related perceptual maintenance. One potential mechanism comes from the synaptic homeostasis hypothesis (SHY), which posits that low frequency slow wave activity during sleep downscales synaptic connections that have become potentiated during wake 66 , 67 . In terms of learning, SHY postulates that encoding during wake increases potentiation of synapses in associated cortical networks, and during subsequent sleep, slow waves “downscale” the synaptic weight, with weaker synapses receiving relatively more downscaling than strong synapses. This process is proposed to increase the signal-to-noise ratio between strong and weak synapses, and, consequently, improve memory processing 68 . It is possible that slow waves may be important for reducing perceptual deterioration through a similar downscaling mechanism 31 .

Prior work has shown that REM sleep is critical for performance improvement on a texture discrimination task 2 , 34 . In the current study, only nap+ showed learning after the nap. Although the majority of both nap+ ( n  = 20) and nap− participants ( n  = 18) had REM sleep, and equivalent amounts of REM sleep at the group level, REM theta activity indicated that perhaps there was a qualitative difference in REM sleep between the groups. Specifically, REM theta power was increased in nap+, and correlated with performance improvement in nap+ only. Theta oscillations are known to be involved in memory processing during wakefulness 69 , and there is now increasing evidence to suggest it is involved in memory reprocessing during sleep. EEG theta activity was increased following learning of word pairs 70 and emotional pictures 71 . Other work has shown that theta was increased after presenting memory reactivation cues during sleep 72 , 73 , and that REM frontal and temporal theta had high discriminative power for decoding what type of information people had learned prior to sleep 74 . Together, the spindle and theta results in nap+ participants suggest that napping may increase the potential for sleep to engage neural mechanisms related to memory reprocessing in these individuals. Furthermore, these data suggest that consolidation processes during NREM sleep (e.g., spindles) and REM sleep (e.g., theta) both contribute to perceptual learning and expand upon the two-process model proposed by Stickgold and colleagues 36 .

Contrary to our hypothesis, the four-week nap practice intervention produced no changes across any of the four outcomes of interest: nap sleep architecture, behavioral performance, sleep inertia, and subjective sleepiness. It is possible that our intervention was not long enough or did not require enough practice (minimum 20 minutes, 3 times per week for four weeks). Indeed, there is considerable variation in how long it takes people to form a habit 75 , with one study showing an average of 66 days (range 18 to 254 days) to form either an eating, drinking or activity behavior, and the length of our intervention was significantly shorter than this. However, it should be noted that habit formation studies measure automaticity of a response given a cue in the environment, which may be different from measuring cognitive benefits from frequent napping. In the current study, we did not collect self-reports that would allow us to examine automaticity of the behavior (e.g., if people came to “look forward to” or “rely” on their nap) in a habit formation framework. However, in regards to the four outcomes, there was no hint of a trend toward a change in performance for nap-individuals assigned to the practice group, suggesting that they were not on a trajectory toward change should the intervention have been extended. One potential caveat is that we were not able to obtain a reliable estimate of nighttime sleep across the intervention. We feel this is due to two factors. First, we asked people to follow their regular sleep schedules (within a two-hour bedtime window and a two-hour wake time window); participants were made aware that if they deviated from this schedule they would become ineligible to continue in the study. Thus, our participants were much more mindful of their nighttime sleep schedule and not entirely subject to “free-living” conditions. This may have restricted our ability to detect variations in overnight sleep characteristics due to nap practice or restriction. Second, the actigraph devices frequently malfunctioned, resulting in substantial missingness and not enough data in each cell (see Supplementary Table  4 ) to run inferential statistics. Therefore, our interpretation of how nap practice or restriction may have affected nighttime sleep is limited to patterns seen in the descriptive statistics and should be approached with caution. Nonetheless, an intriguing pattern that emerges from these data is that participants in intervention groups incongruent with their pre-existing nap preference (e.g., nap+ individuals in the nap restriction condition) showed changes in their nighttime sleep duration across the study. Nap+ individuals who were restricted from napping had an increase of ~17 minutes in overnight average total sleep time, whereas nap− individuals who practiced napping had a decrease of ~16 minutes. However, a similar decrease was seen in nap− individuals who were nap restricted, i.e., congruent with their pre-existing nap preference; nap+ individuals who continued to practice napping only increased ~2 minutes. This suggests that nighttime sleep may be altered to compensate for daytime sleep. However, a study specifically designed to answer this question would be more informative than the current study.

What might be some possible explanations for this individual difference in nap preference? Genetics are likely to play role, and one candidate is the clock gene PERIOD3 , which contains a variable number tandem repeat polymorphism. This polymorphism has been linked to morningness/eveningness preference, delayed sleep phase syndrome, slow wave activity, and waking performance in response to sleep loss 76 . Napping is also related to these factors, and we speculate that PERIOD3 may be one marker of people’s napping phenotype. Another possibility is that nap habits that arise early in development may have an effect on adult habits 23 . A recent study reported that napping was important for learning in preschool children, such that no learning occurred in children restricted from napping 24 . Closer inspection of the data revealed that the decreases in performance were only evident in habitual nappers restricted from napping, whereas no performance decrements were found in non-nappers. A working hypothesis that emerged from this study suggests that habitual nappers have an increased need for frequent consolidation, which may be related to brain maturation during development. Although it is not known how preschool nap habits may be related to adult nap habits, we can extend their hypothesis and posit that there may be functional differences in learning strategies in adults that place differential demands on cognitive load and increase the need for sleep throughout the day. Longitudinal studies that track nap patterns across the lifespan would be informative for understanding how nap habits develop and change (or do not change) over time. Another related question that arises is whether or not these differences in sleep-dependent consolidation extend to nighttime sleep. One possibility is that due to different factors regulating sleep (as discussed above), consolidation mechanisms (e.g., thalamocortical synchrony 46 or spindle refractoriness 77 ) are not optimized during daytime sleep in nap− individuals and consolidation is best accomplished overnight. Finally, further research is needed to determine how the present results may generalize to other populations, such as older adults and clinical samples, and how napping might impact other outcomes related to health and well-being 78 .

Participants

Eighty-three (51 F) healthy, non-smoking adults between the ages of 18 and 35 with no personal history of sleep disorders, neurological, psychological, or other chronic illness gave informed consent to participate in the study. All experimental procedures were approved by the Human Research Review Board at the University of California, Riverside. Methods were carried out in accordance with all guidelines and regulations.

Fifty-eight people participated in the experimental nap protocol explained below, and the twenty-five remaining participants were part of a one-day Wake control group. The Epworth Sleepiness Scale (ESS) 79 and the reduced Morningness-Eveningness Questionnaire (rMEQ) 80 were used to exclude potential participants with excessive daytime sleepiness (ESS score > 10) or extreme chronotypes (rMEQ < 8 or >21). All participants reported regularly going to bed no later than 2AM, waking up no later than 10AM, and getting at least 7 hours of total sleep per night on average. Heavy caffeine users (>3 servings per day) were not enrolled to exclude the possibility of significant withdrawal symptoms during the experiment. Nonetheless, one participant reported experiencing caffeine withdrawal symptoms and was excluded from analyses.

General procedure

This was a five-week protocol that included one week of at-home baseline monitoring and four experimental weeks. Participants completed three in-lab study days, one each at the beginning (Visit 1), middle (Visit 2) and end (Visit 3) of the experimental period, spaced two weeks (14+/−2 days) apart. The study proceeded as follows: (i) Baseline week, (ii) in-lab Visit 1 at the end of the baseline week, with (iii) experimental group assignment (nap Practice or Restriction) occurring at the end of Visit 1 (see Nap Practice and Restriction section below), (iv) two experimental weeks following nap Practice/Restriction, (v) in-lab Visit 2, (vi) two experimental weeks following nap Practice/Restriction, and (vii) in-lab Visit 3. Participants in the Wake group only completed Visit 1.

During the study, participants agreed to maintain their habitual sleep-wake schedule (see above). Adherence to the sleep schedule was tracked with daily online sleep diaries and actigraph wrist monitors (Actiwatch Spectrum, Respironics) for the duration of the study, including the baseline week. Participants were asked to refrain from consuming caffeine, alcohol, and all stimulants for 24 hours prior to and including the study day.

Study Day Procedure

On each in-lab study day, participants reported to the Sleep and Cognition Lab at the University of California, Riverside at 9AM. After verifying adherence to the sleep schedule by checking actigraphy data, participants completed Session 1 of a texture discrimination task (TDT).

At 12:30PM, electrodes were attached for standard polysomnographic (PSG) recording of sleep. All participants were given a two-hour nap opportunity between 1:30PM and 3:30PM to obtain up to 90 min of total sleep time. After reaching 90 min of total sleep time or after the two-hour nap opportunity time had elapsed, regardless of the current sleep stage, an experimenter ended the nap by knocking on the door and entering the bedroom (“nap end”). Lights remained off in the bedroom, and the participant was asked to continue lying supine for five minutes without falling back asleep while post-nap EEG and ECG measurements were made. If a participant spent more than 30 consecutive minutes awake during the nap window then the participant was removed from the bedroom and the nap was terminated.

The descending subtraction test (DST) 29 , 30 was used to probe cognitive functioning due to sleep inertia. The task was administered at four time points, once before the nap (~11AM), and three times after the nap, specifically 5 min, 20 min, and 35 min after “nap end.” The 5 min DST time point was administered in the dark bedroom while the participant was lying supine; after this assessment, lights were turned on and the participant was free to sit up and move around the bedroom. The aim of this procedure was to obtain an initial assessment of post-nap sleep inertia (5 min time point) followed by two subsequent assessments (20 min and 35 min time points) to measure the dissipation of sleep inertia as the participant returned to normal daytime conditions.

At 5PM (Session 2), participants were re-tested on the TDT. Participants also completed the Karolinska Sleepiness Scale (KSS) 81 at three times during the study day – (i) at the end of Session 1 (~11AM), (ii) 10 min post-nap (~3:40PM), and (iii) at the beginning of Session 2 (~5PM). Between sessions (~11AM to 12:30PM and ~4:10PM to 5PM for nap participants, and ~11AM to 5PM for Wake participants), participants left the lab and carried out their day as they normally would, but were instructed to not nap (verified through actigraphy), exercise, or consume caffeine or alcohol. Participants in the Wake group did not nap or complete the DST task or the 10 min post-nap KSS.

Nap Frequency Groups

Due to lack of agreement across studies on how to categorize nappers from non-nappers, we opted to base our distinctions on self-assessment (based on questionnaire answers) and immediate prior evidence of napping (one week of sleep diaries and actigraphy). We obtained information about nap habits in multiple ways. First, during either a telephone or online survey screening questionnaire prior to study enrollment, participants were asked, “Do you take naps during the day? And if so, how many times per week? And how long do you nap?” Second, we counted the number of naps reported in participants’ sleep diaries during the baseline week prior to starting the study, and then verified that these naps occurred by checking the actigraphy data. We defined nap+ as people who reported napping at least once per week [mean 1.54 (SD = 1.03) naps per week], and nap− as napping less than once per week [mean 0.18 (SD = 0.40) naps per week; i.e., never napping or only napping once or twice a month 28 , 44 . When the two sources of information did not match (e.g., a participant reported never napping on the screening survey but then took a nap during the week prior to the study), the participant was interviewed about their nap habits by an experimenter who then made the determination. For example, if the participant reported being a non-napper but they napped because of illness that week, the participant retained nap− status since illness was an out of the ordinary event.

Nap Practice and Restriction

Within each of these nap frequency groups, nap+ and nap− participants were randomly assigned to either a nap Practice or nap Restriction condition. Participants in the Practice group were instructed to nap at least three times per week for a minimum of 20 min for the remaining four weeks of the study (naps in the laboratory on study visits 2 and 3 were allowed to count toward their weekly nap total), whereas those in the Restriction group were instructed to not nap unless asked to take one in the lab during a study visit. Compliance to these conditions was verified by checking sleep diaries and actigraphy. One nap+ participant in the Restriction group took one nap during Week 2 due to illness; this participant’s data were retained in analyses.

Polysomnography (PSG)

PSG data were collected using Astro-Med Grass Heritage Model 15 amplifiers and Grass Gamma software. Eight scalp electroencephalogram (EEG) and two electrooculogram (EOG) electrodes were referenced to unlinked contralateral mastoids (F3/A2, F4/A1, C3/A2, C4/A1, P3/A2, P4/A1, O1/A2, O2/A1, LOC/A2 and ROC/A1), and two electromyogram electrodes were attached under the chin to measure muscle tone. PSG data were digitized at 256 Hz and visually scored in 30-s epochs according to the sleep staging criteria of Rechtschaffen and Kales 82 . Sleep architecture variables included minutes and percentage of Stage 1, Stage 2, slow wave sleep (SWS) and rapid eye movement (REM), as well as total sleep time (TST), sleep latency (SL), and sleep efficiency (SE). Participants were excluded if they did not fall asleep during their first nap ( n  = 2), or if 2 out of 3 naps had TST less than 20 min and SE less than 35% ( n  = 1).

EEG data were preprocessed and analyzed using BrainVision Analyzer 2.0 (BrainProducts, Munich Germany) and Matlab 2011b (MathWorks, Natick MA). EEG data were bandpass filtered between 0.3 and 35 Hz, and a 60 Hz notch filter was also used to eliminate potential background noise. All epochs with artifacts and arousals were identified by visual inspection and rejected. Sleep spindles were automatically detected during Stage 2 and SWS using a wavelet-based algorithm developed by Wamsley and colleagues 57 . In short, the EEG signal underwent a time-frequency transformation using an 8-parameter complex Morlet wavelet. The wavelet scale corresponding approximately to the 10–16 Hz frequency range was extracted and used for spindle detection using Wamsley et al .’s 57 thresholding algorithm. Following spindle detection, spindle densities were calculated by dividing the number of discrete spindle events by minutes spent in each sleep stage at each scalp EEG electrode site. Data for an individual channel were excluded if the channel was determined to be unreliable (e.g., became detached during the recording) based on visual inspection.

Power spectral density (μV 2 /Hz) was calculated by Fast Fourier Transform (FFT), applying a Hanning window to successive 3 sec epochs of sleep with 50% overlap. Spectral power was obtained for the following frequency bands: 0.5–1 Hz (slow oscillations; SO), 1–4 Hz (delta), 4–8 Hz (theta), 8–12 Hz (alpha), 12–15 Hz (sigma), and beta (15–30 Hz) during Stage 2, SWS, NREM (S2 + SWS combined) and REM sleep.

Texture Discrimination Task (TDT)

Participants performed a texture discrimination task (TDT) similar to that developed by Karni and Sagi 38 . Visual stimuli for the TDT were created using the Psychophysics Toolbox 83 , 84 . Each stimulus contained two targets: a central letter (‘T’ or ‘L’), and a peripheral line array (vertical or horizontal orientation) in one of four quadrants (lower left, lower right, upper left, or upper right) at 2.5°−5.9° eccentricity from the center of the screen. The quadrant was counterbalanced across participants and visits. The peripheral array consisted of three diagonal bars that were either arranged in a horizontal or vertical array against a background of horizontally oriented background distracters, which created a texture difference between the target and the background.

An experimental trial consisted of the following sequence of four screens: central fixation cross, target screen for 33 ms, blank screen for a duration between 0 and 600 ms (the inter-stimulus-interval, or ISI), mask for 17 ms, followed by the response time interval (2,000 ms) and feedback (250 ms, red fixation cross with auditory beep for incorrect trials and green fixation cross for correct trials) before the next trial. Participants discriminated two targets per trial by reporting both the letter at central fixation (‘T’ or ‘L’) and the orientation of the peripheral array of three diagonal lines (horizontal or vertical) by making two key presses. The central task controlled for eye movements.

Each block consisted of 25 trials, each with the same ISI. A threshold was determined from the performance across 13 blocks, with a progressively shorter ISI, starting with 600 ms and ending with 0 ms. The specific sequence of ISIs across an entire session was [600, 500, 400, 300, 250, 200, 167, 150, 133, 100, 67, 33, 0]. A psychometric function of percent correct for each block was fit with a Weibull function to determine the ISI at which performance yielded 80% accuracy. TDT performance was calculated as the difference in threshold between Session 1 and Session 2, such that a positive score indicates performance improvement (i.e., decreased threshold in Session 2), whereas a negative score indicates deterioration 43 , 62 .

Participants were given task instructions and practiced the task during an orientation appointment prior to starting the study. During this practice, the peripheral target was located in a quadrant that would not be used during the study. This practice ensured that participants understood the task and aimed to reduce visit order effects due to general task learning that typically occurs the first time a participant performs a task. Additionally, on each study day, participants were allowed to practice an easy version of the task (ISI of 1,000-600 ms) to make sure they were able to discriminate the peripheral target between 90% and 100% correct before starting the actual task.

Descending Subtraction Task (DST)

This task measures cognitive functioning for a brief (3 min) period of time by placing a considerable load on working memory while probing mental computation skills 29 , 30 . To begin, the experimenter gave the participant a three-digit number, for example “865”, which was repeated out loud by the participant. Then the participant was instructed to mentally subtract the number 9 from 865 and to say the answer (856) out loud. This number became the new minuend from which the subtrahend was subtracted. The subtrahend progressively decreased by 1 until it reached a value of 2, after which it returned to 9. Thus, on the next trial the participant should have subtracted the number 8 from 856. Participants were given 3 minutes to complete as many trials as possible. Instructions prompted the participant to work as fast and accurately as possible. The task was administered out loud with the experimenter writing the participant’s responses on a piece of paper attached to a clipboard so that the written responses were not visible to the participant. Participants were allowed to correct any response and were instructed to guess if they asked the experimenter for help. Total number of correct responses and number of correct responses as a proportion of total number of responses were calculated as indices of speed and accuracy, respectively. Difference scores (e.g., 5 min post-nap minus pre-nap performance) were calculated and reported as Δaccuracy and Δspeed.

Data Reduction and Statistical Analyses

Participants whose first TDT threshold (i.e., Visit 1, Session1) was more than 2.5 standard deviations from the mean were flagged as outliers ( n  = 2 for main experiment and n  = 2 for the Wake group; all were poor performers 2.5 standard deviations below the mean). In the main experiment, the two performance outliers together with the two participants removed for poor sleep and caffeine withdrawal were the bottom four TDT performers in the sample. Therefore, we employed equitable trim procedures and also removed the top four Visit 1, Session 1 performers (who were at ceiling). This left 48 participants whose Visit 1 data were analyzed (nap+ n  = 26; nap− n  = 22). We also applied equitable trim to the Wake group and removed the two poor-performing outliers as well as the top two performers, leaving 21 participants in the Wake group. One participant in the nap− group was excluded from DST analyses due to not understanding the task the first time it was performed (Visit 1 training), resulting in an accuracy difference score that was greater than 3 standard deviations above the mean.

Eight of the 48 participants in the nap intervention experiment were dropped or withdrew before study completion [due to illness ( n  = 1), changes in schedules that conflicted with the study ( n  = 3), noncompliance with the sleep-wake schedule ( n  = 2), and unknown reasons ( n  = 2)], leaving 40 participants who completed all three visits. Of the participants who completed the experiment, 21 were assigned to the Practice group (11 nap+, 10 nap−) and 19 were assigned to the Restriction group (9 nap+, 10 nap−). Demographics and other characteristics of our final samples are reported in Supplementary Table  1 .

For spindle results, we focused on centro-parietal regions where spindles (in particular fast spindles) are known to be maximal 85 – 87 and averaged the number of spindles detected over central and parietal electrodes within each hemisphere (i.e., C3-P3 avg and C4-P4 avg ). If no hemispheric differences were evident, we used the grand average (C3-C4-P3-P4 avg ). For power spectral analysis, due to significant topographic differences in power between the frontal and central regions (but no hemispheric differences), we averaged frontal (F3-F4 avg ) and central (C3-C4 avg ) electrodes.

Differences between nap+ and nap− at Visit 1 were tested using independent samples t -tests. Change across visits was tested using mixed-model ANOVA with Visit as a repeated measure and two between-participants factors: Nap Frequency group (nap+/−) and Intervention group (Practice/Restriction). Magnitude of performance change on the TDT was compared to zero (i.e., no change) using one-sample t -tests with difference scores. Bivariate Pearson correlations examined associations between TDT performance and nap sleep features at Visit 1. In order to reduce the number of correlations tested, we focused on power spectra during NREM (Stage 2 + SWS combined) and REM sleep stages, and chose specific frequency bands of interest for each sleep stage (NREM: SO, delta, and sigma and REM: theta). To test for moderation, we ran correlations for nap+ and nap− groups separately, then tested for significant differences in correlation coefficients using the Fisher r -to- z transform and z -test 88 . For analyzing spindles and power spectra across three visits, we used mixed-model ANOVA (see above) and specifically only tested variables that showed significant differences and/or moderation during Visit 1.

Due to the longitudinal nature of this study, there are missing data for sessions and visits, including bad electrodes during nap recordings, missing KSS scores and DST data due to experimenter error, and missing actigraphy data due to watch malfunction. Additionally, not all participants had every stage of sleep in their nap (no SWS: Visit 1 n  = 3, Visit 2 n  = 4, Visit 3 n  = 4; no REM: Visit 1 n  = 10, Visit 2 n  = 4, Visit 3 n  = 5). As such, degrees of freedom vary across analyses.

Electronic supplementary material

Acknowledgements.

Research was supported by funding from the National Institutes of Health RO1AG046646 (S.M.) and T32HL007560 (K.A.D.), National Science Foundation BCS1439210 (S.M.), Office of Naval Research N00014-14-1-0513 (S.M.), and the National Science Foundation Graduate Research Fellowship (E.A.M.). The authors thank Michael Silver and Aaron Seitz for their thoughtful comments on an earlier version of the manuscript.

Author Contributions

E.A.M., K.A.D. and S.C.M. designed the research; E.A.M, N.S., K.A.D., L.N.W., C.P., N.R., S.G. and L.H. performed the research; E.A.M., N.S., K.A.D., N.C., L.N.W. and S.C.M. analyzed data; E.A.M. and S.C.M. drafted the manuscript, and N.S., K.A.D., N.C. and L.N.W. edited the manuscript.

Data Availability

Competing interests.

The authors declare no competing interests.

Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information accompanies this paper at 10.1038/s41598-018-33209-0.

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The Benefits of a Power Nap and How to Take the Perfect Nap – According to Science

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Taking a power nap has many benefits for your brain, heart, stress levels, and mood. A short nap of 10 or 20 minutes in the middle of the day can do wonders for your productivity, alertness, and memory. A power nap will leave you feeling refreshed and increase your energy levels.

Far from being a sign of laziness, the most productive workers use short naps to increase their effectiveness. In fact, more and more companies allow for a midday nap because it can enhance cognitive function. So, if you feel like taking a short snooze in the afternoon, then it’s good to know that you can benefit from a 30-minute power nap.

In this article, you will find out why napping is good for you. You will also learn how long a power nap should be.

What is a Power Nap?

A power nap is a short sleep in the daytime, usually lasting between 10 and 30 minutes. Many people prefer taking a nap in the early afternoon when they naturally feel drowsy or sleepy.

Researchers from Harvard Medical School say that an afternoon nap can help deal with the body’s natural wake and sleep cycle (circadian cycle). Your body experiences a drop in wakefulness in the afternoon, and a nap is perfect to restore alertness. ( 1 )

Scientists also say that a power nap can benefit people who don’t get enough sleep at night. Your afternoon nap can be a good way to “catch up” on lost sleep and restore alertness. In fact, the American Psychological Association says that an afternoon nap is as effective as caffeine in boosting midday alertness. ( 2 )

What is the Perfect Nap Length?

Many studies have tried to establish the perfect nap length. The Journal of Sleep Research reported that short nap length of 10 minutes can give instant benefits. Longer naps lasting 30 minutes also had many benefits that were felt later in the day. Some studies have shown that a 5-minute nap doesn’t have any cognitive benefits. However, napping for 10, 20, or 30 minutes all helped to improve alertness. ( 3 )

Some studies show that a 10-minute nap is the most effective length of time to nap for. ( 3 )

Generally speaking, a short power nap of 10-20 minutes is good for a quick improvement of your alertness and energy level and will enable you to get back to work quickly.

A nap of about 30 minutes will provide you a mental sharpness similar to the 10-20 minute nap, with that sharpness lasting a bit longer, but the downside is that people tend to feel groggy immediately after this kind of nap.

A longer nap of 60 minutes is good for your cognitive memory. It can help you remember faces, names and facts, but the downside is some grogginess upon waking.

A long nap of 90 or more can provide you a full sleep cycle which improves procedural memory (such as riding a bike or playing the piano) and creativity. Waking up after it usually has minimal amount of grogginess.

So to summarize, if you are looking for a quick boost or recharge, you are looking at a short nap length of about 10-20 minutes. However if you are looking for deeper sleep rejuvenation, you are looking at a longer nap of about 60-90 minutes.

The Benefits of a Power Nap

Let’s look in more detail how power naps can work for you to improve memory, increase learning, become more efficient and generally function better.

Power Nap Improves Alertness

One of the instant benefits of taking an afternoon power nap is that you will feel more alert.

Researchers have found that a brief power nap of between 5 and 15 minutes can make you immediately feel more alert. One study showed that the effects of a short nap can last for up to 3 hours. A longer nap of 30 minutes also helped to improve alertness with the effects lasting for many hours. ( 4 )

One 2019 study found that a 30-minute nap at 1:00 p.m. boosted cognitive function and restored alertness. The study also showed that an afternoon nap can help to improve physical performance and reduce fatigue. ( 5 )

Some studies show that napping is as effective as drinking coffee to increase alertness. However, other studies reveal that the benefits of a 15-minute nap can be enhanced by having a coffee just before your nap or washing your face. ( 6 )

Another study showed that taking a cup of coffee after a 15-minute nap can help make you more alert when driving. ( 7 )

Power Nap Improves Productivity

Enjoying a short nap in the afternoon can also help boost your productivity at work.

The journal PLoS One found that the best time to nap is between 2 p.m. and 4 p.m. which is when you may feel the sleepiest. Researchers have found that napping for 15 to 45 minutes between 12:30 and 14:00 is the most effective time to increase productivity. ( 8 )

However, a long nap seemed to negatively impact on alertness and productivity.

One study found that napping for 30 minutes or less was good to enhance learning ability and performance. ( 9 )

A small study found that 20 minutes nap in the mid-afternoon had positive effects upon maintaining daytime vigilance level, and improved performance level and self-confidence of the participants in their task performance. ( 26 )

Power Napping Improves Memory

The benefits to your cognitive function of taking a nap after lunch can also help to boost your memory.

Studies have shown that regular napping can benefit your long-term and short-term memory.

A 2019 study published in the journal Sleep found that napping can help to improve memory function over the long-term. Taking a nap was more effective than taking a break and helped young adults retain more information when studying. ( 10 )

Studies have also shown that a quick nap during the day can benefit short-term memory. For example, a study involving 145 female shift workers found that those who napped had better alertness and cognitive function than the non-nappers. ( 11 )

Another study reported that napping after lunch benefits short-term memory, accuracy, and alertness. ( 12 )

Further reading: Proven Brain Foods to Boost Brain Power, Focus and Memory .

Power Naps Boost Endurance Performance

Dozing after lunch for 20 minutes or so can also improve your energy levels and increase your performance.

The European Journal of Sport Science in 2018 reported that athletes who napped for between 20 and 30 minutes performed better. Napping in the afternoon was a good way to reduce the effects of sleep deprivation . ( 13 )

Power Nap Promotes Good Heart Health

A meta-analysis on the effects of napping on your heart health found that a short nap can lower your risk of heart disease. The perfect length of time for a nap to promote good heart health was under 30 minutes. Interestingly, regularly napping for an hour or more during the day was associated with an increased risk of heart disease. ( 14 )

One of the reasons why a power nap is good for your heart is that it helps improve your circadian rhythm. This has been shown to lower stress levels and blood pressure – both of which can impact on your health. ( 14 )

The researchers believe that an afternoon nap may contribute to stress-releasing process, which can help reduce mortality from coronary heart disease.

A large research from the Harvard School of Public Health and the University of Athens Medical School found that midday napping reduced coronary mortality by about one third among men and women. The study found that people who regularly took naps at least three times per week for an average of at least 30 minutes, had a 37% lower coronary mortality than those not taking naps. ( 25 )

Find out how  the cardiac diet can be good for your heart.

Power Nap May Help Control Blood Pressure

Enjoying a short siesta can also be good to manage high blood pressure.

For example, one study found that blood pressure drops during a short afternoon sleep when compared to being awake. ( 15 )

Other studies have shown that power napping in the afternoon can be more beneficial for your blood pressure than just relaxing while awake. ( 16 )

Learn about other natural ways to manage hypertension naturally and prevent strokes or heart disease.

Power Nap Boosts Your Immunity

Having a power nap after lunch is also good for your health in general because it can boost your immune system.

Researchers have come to realize that getting enough sleep is necessary to strengthen your immune system. There is also evidence that a brief nap can also give your immunity a needed boost.

One study found that napping is a good way to offset some of the negative effects sleep deprivation has on your immunity. Getting a 30-minute nap helps to normalize your body’s immune response. ( 17 )

A power nap is one of the great hacks to quickly get your immunity working as it should. You can also learn what else you can do to prevent infection due to a weakened immune system.

Power Naps to Help Relieve Stress

A 30-minute power nap can also be good to deal better with stress and avoid the consequences of being constantly stressed .

Getting enough sleep helps your body produce hormones that are associated with lower stress levels. Taking a nap can help to normalize hormone levels if you haven’t had enough sleep.

The Journal of Clinical Endocrinology & Metabolism reported that napping has a stress-releasing effect. From various reports, it seems that the ideal nap time to relieve stress is around 30 minutes. The researchers also found that this nap length helped boost immunity and cardiovascular health. ( 18 )

A study involving night-shift workers found that taking two 15-minute naps helped to relieve tension and calm the nerves. ( 19 )

Other studies have found that short naps are good for helping to reduce psychological and physiological strain. ( 20 )

Learn more about why getting an afternoon nap is just one of the effective remedies for dealing with anxiety and stress.

Power Nap Could Help Improve Depression and Boost Mood

Having a short sleep in the afternoon can be one of the ways to improve your mood and manage depression.

One trial involving people with depression found that napping after a sleepless night was beneficial. The patients napped for 10 minutes during the day and researchers noted they had fewer symptoms of depression after the nap. ( 21 )

Another study found that a power nap has many benefits for people with depression. The study found that napping between 2 p.m. and 3:30 p.m. helped to improve the general well-being of depressed people. ( 22 )

Taking a nap in the afternoon can also boost the mood of people who don’t have depression. One small study found that a short 20-minute nap helped to boost mood and have a positive effect on cognitive function. ( 23 )

For more ways to deal with mild depression naturally, please read this article on natural remedies for anxiety and depression . You may also find that serotonin supplements can help if you suffer from depression.

Power Napping Increases Testosterone in Men

A power nap after lunch can be good for male sexual health because it boosts testosterone levels.

Studies into the effects of hormone production during sleep have found that levels of testosterone increase while sleeping. This is one reason why men who regularly nap seem to have higher testosterone levels in the afternoon. ( 24 )

Tips for the Perfect Nap

Power naps can really help to improve your mood, alertness, learning ability, and general well-being.

What can you do to enjoy the perfect power nap? And when is the best time to go for a nap?

Most studies show that your body naturally becomes drowsier in the 2 or 3 hours after lunch. So, generally, power naps are best enjoyed in the early afternoon or not long after eating lunch.

Most of us feel tired between 1 and 4 pm, so try to fit your nap during those hours. Don’t make it later otherwise it can interfere with your ability to fall asleep at bedtime.

Here are some ways to enjoy the perfect nap:

Don’t nap too long . A power nap is never meant to be too long. Usually, napping between 10 and 30 minutes is the ideal length of time for a nap. If you nap too long, you may feel drowsy for the rest of the day.

When taking shorter naps , it is recommended to sleep partially upright to make it easier to wake up and to avoid falling into a deeper sleep.

Create the right environment . You will fall asleep for a short nap easier if you are in a dark place that isn’t too warm.

Time your caffeine right . Some power nappers find that taking a cup of coffee right before napping is effective. Studies have shown that this helps you to wake up more alert after your power nap. ( 6 )

Try relaxing beverages . You can avoid the stimulating effect of caffeine by taking a relaxing herbal tea before or after your power nap.

Have a light snack . Did you know that there are some foods that make you sleepy ? Take a glass of warm milk or eat a banana to help you fall asleep faster.

Remove distractions . Make sure that you won’t be distracted during your 10, 20, or 30-minute power nap. So, put your phone on a flight mode if using it as an alarm clock.

Try the 4-7-8 exercise to fall asleep . Learn more here about this exercise that will help you fall asleep in no time at all.

Try to nap at a regular time . If your schedule allows for it, try to schedule a power nap for the same time every day. This way you teach your body to expect the nap and you may find it easier to fall asleep.

Related Articles:

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The science behind power naps, and why they're so damn good for you

The stigma against napping is finally starting to wane — and for good reason. Taking a timeout to sleep during the day does much more than just give us a quick energy boost. It also confers some serious cognitive and health advantages as well. Here’s what the latest science tells us.

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Unlike 85% of all mammalian species, humans sleep just once a day. Scientists aren’t sure if we’re naturally monophasic (as opposed to polyphasic) or if it’s modern society that has made us so. Regardless, it’s clear that we’re not getting enough sleep. Nearly a third of us say we're simply not getting enough of it.

Power naps can alleviate our so-called sleep deficits , but they can also boost our brains, including improvements to creative problem solving, verbal memory, perceptual learning, object learning, and statistical learning. They help us with math, logical reasoning, our reaction times, and symbol recognition. Naps improve our mood and feelings of sleepiness and fatigue. Not only that, napping is good for our heart, blood pressure, stress levels, and surprisingly, even weight management.

Now, before we get into the science behind many of these benefits, it’s important to define what we mean by a power nap — and how to do it right.

Different types of naps

A power nap is a sleep session that happens during the day (ideally between 1:00 to 4:00 PM) lasting between 10 and 30 minutes. Any longer and you run the risk of developing “sleep inertia” — that unpleasant groggy feeling that takes a considerable amount of time to shake off. And naps later than 4:00 PM can disrupt your regular nighttime sleep.

But these aren’t hard-and-fast rules. Some sleep scientists, like the University of California, Riverside’s Sara Mednick — author of Take a Nap! Change your Life — says that naps at different durations result in different benefits. For example, a 10 to 20 minute nap will provide a quick boost of alertness while mitigating the onset of sleep inertia. At the same time, she’s not a huge fan of the 30 minute nap, saying that recovery often takes too long.

Interestingly, research has shown that six-minute naps, known as ultra-short sleep episodes, can improve declarative memory (i.e. a type of long-term memory that pertains to our ability to recall facts and knowledge).

Mednick also makes the case for 60 minute naps, which are also good for cognitive memory processing. But to understand why this is the case, we need to look at how sleep cycles work.

While we’re asleep, the brain cycles through a pattern lasting about 90 to 120 minutes. These stages include non-rapid eye movement ( NREM ) and rapid eye movement (REM) (which is associated with dreaming ). During NREM sleep we enter into slow-wave sleep, which is the deepest kind. Slow-wave sleep helps us remember facts, places, and faces, which is why the 60 minute nap helps us in this regard.

There’s also the 90 minute nap (but seriously, who has that much time during the day?). That’s one complete sleep cycle. Mednick says these epic naps can aid in creativity and emotional and procedural memory, while resulting in a minimal amount of sleep inertia.

Check out Sara Mednick’s TEDxYCRSalon talk:

Naps themselves can be broken down into four types:

• Planned napping : Also known as preemptive napping, it involves taking a nap before you get sleepy. It’s a good thing to do if you know you’re going to have a late night.
• Emergency napping : This is exactly as it sounds — taking a nap when you’re so sleepy that you can’t properly engage in your current activity. This is the kind of nap that’s advisable to take when you get sleepy behind the wheel or while operating dangerous machinery.
• Habitual napping : This is the practice of taking a nap at the same time every day.
• Appetitive napping : The act of napping strictly for enjoyment.

Immediate Cognitive Benefits

As noted, napping is particularly great for alertness, learning, memory, and performance — and we’ve known this now for several decades.

A groundbreaking NASA study from 1995 ( pdf ) looked at the beneficial effects of napping on 747 pilots. Each participant was allowed to nap for 40 minutes during the day, sleeping on average for 25.8 minutes (which is just about right). Nappers "demonstrated vigilance performance improvements from 16% in median reaction time to 34% in lapses compared to the No-Rest Group."

Indeed, napping while on the job is not a bad idea. Planned naps have been shown to improve alertness and performance in emergency department physicians and nurses , along with first-year medical students . What these and other studies are showing is that naps can restore our attention, the quality of our work, while also helping us reduce our mistakes. It also improves our ability to learn while on the job. What’s more, the effects of napping extend a few hours into the day.

Thankfully, companies are starting to catch on. Modern firms are increasingly creating sleep spaces while providing an encouraging, supportive environment. They’re also setting up the right equipment for sleeping on the job; Christopher Lindholst of MetroNaps has installed specially designed sleeping pods for Google, Huffington Post, the Arizona Diamondbacks baseball teams, and other firms.

Think that grabbing a cup of coffee in the middle of the afternoon does just as well? Think again.

A 2008 study showed that naps are better than caffeine when it comes to improving verbal memory, motor skills, and perceptual learning. Afternoon naps improved free recall memory compared to the caffeine group after both 20 minutes and seven hour intervals, while resulting in improved learning on physical tasks than caffeine. It should be noted, however, that the researchers had their participants nap between 60 and 90 minutes. A cup of joe might be a tad more efficient . But as noted in the study, caffeine has been known to impair motor sequence learning and declarative verbal memory.

Other Health Benefits

Naps can also reduce stress, which is not a small thing as far as our overall health is concerned.

For example, napping can help us manage our blood pressure . Daytime sleep can confer heart-related benefits by accelerating cardiovascular recovery after bouts of psychological stress. Researchers discovered that a 45 minute nap literally lowers blood pressure.

An extensive 2007 study came to a related conclusion. For over six years, a research team tracked 23,681 people in Greece, none of whom suffered from coronary heart disease, stroke, or cancer. People who napped at least three times per week for an average of 30 minutes a day had a 37% lower chance of dying from a heart-related disease. This held particularly true for working men (too few women died to draw any meaningful conclusions).

And according to a letter published in the British Journal of Nutrition , obesity prevention may be as simple as turning off the television and having a nap . The authors write:

Like TV watching, sleep is an activity characterised by prolonged periods of reduced energy expenditure. Yet accumulating evidence suggests that adequate sleep protects against obesity, while short sleep duration is prospectively associated with increases in both total and abdominal adiposity in adults and children. These contrasting lines of evidence suggest that if an individual is planning to spend an afternoon on the couch, they are better off asleep than watching TV. While the above may seem like an odd public health message, it is nonetheless supported by a growing body of research suggesting that TV viewing and sleep have contrasting effects on energy balance and weight maintenance

Don’t forget the children

Lastly, it should be noted that napping is good for people of all ages, but particularly children. Sadly, however, they’re napping less and less.

After small children graduate from toddlerhood, they typically transition from biphasic (twice a day) to monophasic sleep (once a day). Some of this has to do with the children themselves, who are always on the go and reluctant to go down for nap. But it’s also societal problem. And in fact, because there’s a lack of science on the matter, some jurisdictions are looking to eliminate the preschool nap citing increasing curriculum demands (yes, really).

But according to a brand new study conducted by Rebecca Spencer , daytime sleep is critical for effective learning in young children. Classroom naps boosts the learning capabilities of preschool children by enhancing the memories they acquired earlier in the day. Conversely, children experience deficits in performance when they’re nap-deprived — deficits that cannot be recovered during subsequence overnight sleep. The researchers conclude by saying that, “distributed sleep is critical in early learning; when short-term memory stores are limited, memory consolidation must take place frequently.” Moreover, naps help children of all ages.

Other studies have reached similar conclusions. Naps help infants learn the rules of abstract language and when storing long-term memory . And to virtually no parent’s surprise, sleep-deprived children between the ages of 2 and 3 “ show more anxiety, less joy and interest and a poorer understanding of how to solve problems… "

Thankfully, napping is starting to catch on. Estimates vary, but surveys show that the frequency of napping (at least once a week) ranges from 36% to 80%. A recent “Sleep in America” poll showed that 46% of respondents napped at least twice in the last month, with an average nap duration lasting about one hour.

Additional reporting by Joseph Bennington-Castro.

Other sources: wsj | national sleep foundation | benefits of napping in healthy adults: journal of sleep research ., images: maxym /shutterstock; michael pettigrew/shutterstock; creativa/shutterstock..

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Article Contents

“why should someone get paid to sleep on the job”, “i don’t have time to nap. i have too much work.”, “you must be lazy if you take naps.”, acknowledgments.

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Challenging the stigma of workplace napping

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Sara E Alger, Allison J Brager, Vincent F Capaldi, Challenging the stigma of workplace napping, Sleep , Volume 42, Issue 8, August 2019, zsz097, https://doi.org/10.1093/sleep/zsz097

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“Why should someone get paid to sleep on the job?” “I don’t have time to nap. I have too much work to do.” “You must be lazy if you take naps.” Despite growing awareness and appreciation of the value of sleep as well as resources, such as books by prominent sleep researchers [ 1 , 2 ], directed toward general public consumption, there still remains a stigma related to napping. This negative perception is compounded when considering napping during working hours, resulting in frequently heard comments and questions like those above. How can we as sleep scientists, the subject matter experts who appreciate the broad scope of benefits to physical, emotional, and cognitive health conferred by naps, combat the negative optics of workplace napping? We begin by addressing these points of contention.

While napping is essential for the health and development of young children, for many people it carries into adulthood as a habitual practice. In the United States, however, most working adults are not able to fit a nap into the day, largely due work demands and employer resistance to change workplace culture. Yet outside the United States, there are culturally different attitudes toward napping. In Spain and Italy, mid-afternoon breaks known as the siesta and riposo , respectively, are scheduled during the workday wherein napping often occurs. To suggest such a revision in business hours for the modern US workplace, however, may be unreasonable. Some Asian countries, such as China and Japan, encourage napping on the job. Japanese practice inemuri , sleeping or daydreaming during work, which is viewed as a sign of dedication to work to the point of exhaustion. Japanese businessmen also frequent capsule hotels containing sleep pods in order to reap the recuperative value of sleep during multi-day business negotiations. In the United States, coffee breaks and time spent browsing social media occur in part to boost and re-direct mental focus. What if more employers replaced coffee breaks with scheduled naps? Dr. James B. Maas, who coined the term “power nap,” encourages prioritizing sleep whenever possible, including implementing office napping policies [ 2 ]. Employees already seek out covert naps, and internet tips for “sneaking in a nap at work” reveal unsanitary (restroom) and uncomfortable (car) locations as top sites for napping. If employers embraced workplace napping, this option could produce a comparatively more marked and sustained increase in productivity. As many are sleep restricted during the work week, napping may confer performance advantages similar to data reported in the January 2019 issue of SLEEP [ 3 ].

Perhaps a better question may be “What is the cost of working fatigued?” According to a fatigue cost estimator from the National Safety Council and Brigham and Women’s Sleep Matters Initiative, health-related cost of lost productivity is $136 billion a year. Further, a reported 70% of Americans regularly experience insufficient sleep. Sleep loss, especially in the presence of underlying sleep disorders, results in reduced workplace productivity and increased absenteeism, health care expenditures, workplace accidents and injuries, and motor vehicle accidents during commutes. Thus, it may be costing employers more in the long-term not to allow workers to increase total daily sleep time and alertness with a brief nap during working hours than to prevent napping when needed.

During an average work afternoon, a disproportion of the circadian alerting signal to the rising homeostatic sleep pressure occurs, resulting in increased sleepiness and reduced alertness. These factors, along with other impacted cognitive and emotional performance metrics, result in decreased productivity. There is a wealth of evidence that brief daytime naps of 10–20 minutes decrease subjective sleepiness, increase objective alertness, and improve cognitive performance (for review [ 4 , 5 ]). Daytime napping facilitates creative problem solving and logical reasoning, boosts the capacity for future learning, and consolidates memories (for review [ 6 ]). These benefits are not restricted to those experiencing sleep deprivation. Even in well-rested individuals, napping can enhance alertness, performance, and productivity for several hours [ 4 ]. Daytime naps also allow for the regulation of emotions [ 7 ], relieve stress, and strengthen immune system function, reducing levels of the stress hormone norepinephrine and normalizing levels of interleukin-6 an immune-regulating molecule [ 8 ]. Taken together, allowing time to nap during the workday and reap the collective benefits will result in greater productivity and quality output rather than simply pushing through the fatigue, producing sub-standard work.

This statement reflects the most damaging and pervasive stigma placed upon napping. Sleep deprivation, in some populations, is still considered a point of pride and a reflection of toughness. However, this argument is based largely in ignorance and companies are beginning a movement to counteract it. Along with recommendations to sleep 7–9 hours at night, daytime naps are being integrated into workplace culture in the world’s largest grossing tech, consulting, media, and retail companies: Google, Uber, Nike, Cisco, Zappos, Huffington Post, PricewaterhouseCoopers, Proctor & Gamble, and Ben & Jerry’s. Not only do these companies encourage workplace naps, but they provide accommodations, such as rooms secluded for the purpose of napping, often equipped with nap pods or beds. Even government agencies focused on fatigue countermeasures (e.g. NASA and the Federal Aviation Administration) provide napping pods in which employees can rest and restore cognitive and emotional resources.

The challenge is to continue the spread of information regarding the wealth of benefits of napping to combat the numerous physical, mental, and financial consequences of fatigue. The long-term plan is to normalize and implement scheduled napping during working hours. One of the first steps in this process is to gather empirical evidence demonstrating the relative increase to workplace productivity with a brief nap compared to soldiering on without it. There exists a plethora of laboratory-based napping experiments. However, there is a dearth of applied research in the workplace examining the impact of a napping intervention on occupationally relevant performance measures. Building and disseminating this evidence will push us closer to a society that values napping and works to remove the stigma of taking that mid-day snooze.

This material has been reviewed by the Walter Reed Army Institute of Research, and there is no objection to its presentation and/or publication. The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the position of the Department of the Army or the Department of Defense.

None declared.

Conflict of interest statement . None declared.

The authors thank Dr. Tina Burke for her suggestions and amendments.

Mednick SC , et al.  Take a Nap!: Change Your Life . New York, NY : Workman Publishing Company ; 2006 .

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Maas JB , et al.  Power Sleep: The Revolutionary Program that Prepares Your Mind for Peak Performance . New York : Villard . 1998 .

Cousins JN , et al.  A split-sleep schedule rescues short-term topographical memory after multiple nights of sleep restriction . Sleep . 2019 ; 42 ( 4 ). doi. 10.1093/sleep/zsz018

Ficca G , et al.  Naps, cognition and performance . Sleep Med Rev. 2010 ; 14 ( 4 ): 249 – 258 .

Hilditch CJ , et al.  A review of short naps and sleep inertia: do naps of 30 min or less really avoid sleep inertia and slow-wave sleep? Sleep Med. 2017 ; 32 : 176 – 190 .

Mantua J , et al.  Exploring the nap paradox: are mid-day sleep bouts a friend or foe? Sleep Med. 2017 ; 37 : 88 – 97 .

Gujar N , et al.  A role for REM sleep in recalibrating the sensitivity of the human brain to specific emotions . Cereb Cortex. 2011 ; 21 ( 1 ): 115 – 123 .

Faraut B , et al.  Napping reverses the salivary interleukin-6 and urinary norepinephrine changes induced by sleep restriction . J Clin Endocrinol Metab. 2015 ; 100 ( 3 ): E416 – E426 .

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Your Employer should encourage Napping at Work – Here’s why

The uninterrupted, eight-hour workday as we know it is a fairly new invention. Before the 19th century, most workers enjoyed a long midday break. Industrialization did away with the siesta, but at a cost, as we humans are still genetically hardwired for daytime sleep. With a global workforce that is increasingly sleep-deprived, bringing back daytime naps has never been more important. 

Reason 1: Employees are sleep deprived

The first reason why employers should allow napping at work is very straightforward: Employees are sleep deprived. 

Estimates say as many as 30% of adults globally suffer from insomnia. Covid-19 should has increased that number even higher. The pandemic has been shown to be directly related to climbs in insomnia rates (a syndrome sometimes called coronasomnia).

It is important to remember that everybody experiences a dip in their circadian rhythm around midday. In other words, most adults would likely nap in the afternoon if circumstances allowed them.  

Restworks’ 2021 research indicates that employees nap more when working from home – and that they would at the office too, if they could. In fact, 70% of workers agree that employers should encourage naps at the workplace.

Chronic sleep deprivation comes with serious health consequences. It also has a devastating effect on productivity, estimated to cost businesses billions of dollars each year. Sleep-deprived workers are sick and absent from work more frequently. They get less done while at work, and are significantly more prone to making errors and experiencing accidents. For this reason, sleep health is an issue that companies should address.

Reason 2: Naps make people more productive

Naps are not only an effective way to combat sleep deprivation among employees. They are also more performance-enhancing than caffeine . Research clearly shows that after a 20-minute power nap, alertness, cognition, and mood improve significantly – an effect that lasts throughout the day.

The positive effects of napping don’t stop here. For example, there is promising data to support that naps help against anxiety – a major health issue among health care personnel, among others. Likewise, napping effectively mitigates burnout, which affects up to 77% of the workforce .

The benefits of napping at work more than outweigh the time spent sleeping. Encouraging a short nap at work should be seen as an investment, rather than an expense. 

Reason 3: Workplaces that offer naps are more attractive to job seekers

Some of the world’s most well-known companies already do it – and if you want to attract a talented workforce, so should you. 

Surveys indicate that job candidates are more prone to choose a company that offers the opportunity to nap during the day at their new workplace. They would feel more loyal towards an employer who would let them nap. In these days when US workers are quitting their jobs at record rates , standing out from the competition in the job market should be a high priority. 

Nike, PricewaterhouseCoopers, Zappos, Facebook, and Google are among the companies that have chosen to invest in their employees’ sleep health. Will your company be next?

Nap facilities for your workplace

Restworks is the world’s leading provider of rest and nap facilities for the workplace. Our selection includes the famous EnergyPod power nap chair , as well as the GoSleep airport sleep pod . Explore our range of nap pods, recliners, and massage chairs. You are also welcome to contact us if you want to know more about how we can help your business establish rest facilities.

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A student protester's guide to last-minute essay writing

I f those trips down to the demos in Westminster have left you behind schedule for your end-of-term assignment, you may well be forced to write in the small hours this week. Here's how to pull it off safely and successfully.

12am: Get as far away from your bed as possible

Before you begin, avoid warmth and soft furnishings. Propped up on pillows in the glow of a laptop may feel like savvy ergonomics, but your keyboard will start to look pillow-like by midnight, and 418 pages of the word "gf64444444444444444444" will detract from the force of your argument. You could try the kitchen. Or Krakow. But your industrially lit 24-hour campus library should do the trick.

12:25am: Take a catnap

Thomas Edison used to catnap through the night with a steel ball in his hand. As he relaxed and the ball dropped, he would wake up, usually with fresh ideas. "Caffeine and a short nap make a very effective combination," says Jim Horne, director of the Loughborough Sleep Research Centre. "Have the coffee first. This takes about 20 minutes to work, so take a 15-minute nap. Use an alarm to wake up and avoid deep sleep kicking in. Do this twice throughout the night."

12.56am: Reduce your internet options

Temporarily block Twitter, Spotify, Group Hug, YouTube, 4od and anything else that distracts you. Constantly updating your word count on Facebook may feel like fun, but to everyone else you'll look like you're constantly updating your word count on Facebook.

1-3am: Now write your essay. No, really

You've widened your margins, subtly enlarged your font and filled your bibliography with references of such profound obscurity that no one will notice you're missing 3,000 words. It's time to brainstorm, outline, carve words, followed by more words, into that milk-white oblivion that taunts you. Speed-read articles. Key-word Google Books. Remember texts you love and draw comparisons. Reword. Expound. Invent. Neologise. Get excited. Find a problem you can relish and keep writing. While others flit from point to point, your impassioned and meticulous analysis of a single contention is music to a marker's eyes.

3-5am: Get lost in your analysis, your characters, your world Write like you're trying to convince the most stubborn grammarian about truth, or heartless alien invaders about love. Don't overload with examples – be creative with the ones you have. Detail will save your life, but don't waste time perfecting sentences – get the bulk down first and clean up later. "The progress of any writer," said Ted Hughes, "is marked by those moments when he manages to outwit his own inner police system." Outwit your own inner police system. Expect progress. Ted says so.

5:01am: Don't cheat

It's about now that websites such as easyessay.co.uk will start to look tempting. And you may sleep easier knowing that a dubiously accredited Italian yoga instructor is writing about Joyce instead of you. But the guilt will keep you up between now and results day. And you'll toss and turn the night before graduation, job interviews, promotions, dinner parties, children's birthdays, family funerals . . . you get the idea.

5.17am: Don't die

Sounds obvious, but dying at your computer is definitely trending. And however uncool it may seem to "pass on" during a five-day stint at World of Warcraft, it will be much more embarrassing to die explaining perspectivism to no one in particular. So be careful. Stay hydrated. Blink occasionally. And keep writing.

5.45am: Eat something simple

"There are no foods that are particularly good at promoting alertness," says Horne. "But avoid heavy and fatty meals in the small hours. Avoid very sugary drinks that don't contain caffeine, too. Sugar is not very effective in combating sleepiness." Fun fact: an apple provides you with more energy than a cup of coffee. Now stick the kettle on.

5.46am: Delight in being a piece of living research

If you happen to be "fatigue resistant" you should now be enjoying the enhanced concentration, creative upwelling and euphoric oneness that sleep deprivation can bring. If not, try talking yourself into it. "Conversation keeps you awake," says Horne. "So talk to a friend or even to yourself – no one will hear you."

6am: Console yourself with lists of writers who stuck it out

Robert Frost was acquainted with the night. Dumas, Kafka, Dickens, Coleridge, Sartre, Poe and Breton night-walked and trance-wrote their way to literary distinction. John and Paul wrote A Hard Day's Night in the small hours. Herman the Recluse, atoning for broken monastic vows, is said to have written the Codex Gigas on 320 sheets of calfskin during a single night in 1229. True, he'd sold his soul to the Devil, but you're missing out on a live Twitter feed, so it's swings and roundabouts.

7am: Remember – art is never finished, only abandoned

Once you accept there's no more you can do, print it off and get to the submissions office quick. Horne: "You're not fit to drive if you've had less than five hours sleep, so don't risk it. Grab some exercise." Pop it in with the breeziness that comes from being top of your marker's pile. Back home, unblock Facebook and start buffering The Inbetweeners. And then sleep. Get as near to your bed as you can. Euphoric oneness doesn't come close.

Matt Shoard teaches creative writing at the University of Kent.

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Power Napping on the Job: It May Help Your Company Save Money

Last Updated on January 11, 2024

Written by Mark Mattei

Written by Mark Mattei, Content Writer

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Find out from our sleep team about the benefits and cons of power napping on the job.

Research suggests that taking a nap at work actually improves performance, so, why does the sleep-work relationship have such a negative stigma?

As a 16-year-old, I often worked a 12-hour Saturday shift at the local grocery store. This included the typical duties for a teenager’s first job, taking out the trash, and unclogging toilets. Good times.

One afternoon, I finished my duties with several hours to spare. I was exhausted, so I headed to my car to take a power snooze. No one would ever know.

About 10 minutes into my slumber, I jolted awake to someone tapping on my window. It was my manager. I had made the mistake of parking right next to her.

Inside the store, I was publicly scolded. “Sleeping at work is not acceptable,” she announced. “Anyone caught doing so will be let go.” This is every employee’s greatest fear, getting the sack because you were power napping on the job.

Fast forward 10 years. Here I am researching for this article but before writing it, I make a point to rest for a half hour. In fact, I do this for 30 minutes at work almost every day, and I don’t even have to hide it from my managers.

So, why am I not only allowed but encouraged by my bosses to do this? (Helps that we run a sleep website!) It’s because research shows that this practice actually makes for more productive employees.

What Is a Power Nap?

A power nap typically lasts 20 to 30 minutes and takes the sleeper into phases 1 and 2 of the sleep cycle. This type of rest helps re-energize both the mind and body, helping workers feel ready to go when they wake up.

Make sure to set an alarm. Napping for more than 30 minutes could have you going into slow wave sleep, or more commonly called “deep sleep”. This could leave you waking up even more tired than before.

The amount of time needed varies from person to person, and some people might need a full  30 minutes. Do some testing at home to figure out what your ideal power rest time is. You will know when you got it because you’ll wake up feeling renewed with energy. “Voluntary napping, on the other hand, is not a sign of sleep deprivation, illness, or aging. In fact, a “power nap” can be helpful as well as enjoyable. Many studies of shift workers and other volunteers have reported that a nap as brief as 20 minutes can improve alertness, psychomotor performance, and mood.”

[2] Harvard Medical School

Sleeping at Work Is a Growing Trend

Catching some Zzz’s on the job is becoming more acceptable every year, but the practice has not gained the traction that workers need and hope for.

A 2002 study showed that job performance improves after a 30-minute rest. A 2003 experiment displays nearly the same finding, while a 2010 publication indicates that power sleep improves cognitive function.

It’s now 2021, so why are there still so many companies that fail to see the benefit of this practice?

The principal reason is that they probably have no idea. “Lots of research shows that a nap of about 20 minutes in the afternoon has a positive effect on attention vigilance mood and alertness” — Dr. Rita Aouad, M.D. [3]

Benefit for the Employer

Most business leaders do not realize that sleep deprivation in the workplace costs U.S. economy $411 billion a year. If you are an employer, this gives you something to consider, right?

It could be easy to shrug off these numbers and think, “this doesn’t affect my company.” Based on the statistic that 1 in 3 employed adults do not get enough sleep, chances are it does affect your business. More info

Read more about potential sleep deprivation costs .

With sleep deprivation negatively influencing the global economy at nearly 3% GDP, and studies showing that instituting sleep-friendly policies can improve productivity by 34% and alertness by up to 100%, allowing employees to rest in the workplace stands to help companies make more money.

And if you think simply adding a coffee machine to the office is a fix, another study found that napping is a more powerful tool than caffeine to improve overall memory and cognitive function. Then again, you can always consider the popular coffee nap .

The RAND Corporation instructs employers to “recognize the importance of sleep and the employer’s role in its promotion.” Doing so could drastically change your workplace and directly influence profits. Researchers studying the effects of daily 30-minute naps at a data entry company found that after several weeks, employees were 2.3 percent more productive. [4]

Benefits for the Napper

When 1:00 p.m. rolls around and you feel like you might pass out at your desk, taking 20 to 30 minutes to sleep might just help you get through the day. Not only may this give you the energy you need, but a nap can help improve your overall work performance, which may help you stand out as an exceptional employee.

Apart from work, if the worker is not getting enough rest at home, supplementing missed sleep with a daytime snooze can be beneficial to their health . Here are just a few ways:

Lower Blood Pressure

“If someone has the luxury to take a nap during the day, it may also have benefits for high blood pressure, “– Dr. Manolis Kallistratos, M.D. [5]

Relieve Stress and Support Heart Health

“Our findings suggest that daytime sleep may offer cardiovascular benefit by accelerating cardiovascular recovery following mental stressors” — Ryan Brindle, PH.D. and Sarah Conklin, Ph.D. [6]

Improve Memory

“A short nap at the office or in school is enough to significantly improve learning success. Whenever people are in a learning environment, we should think seriously about the positive effects of sleep.” — Alex Mecklinger, PH.D. [7]

Improve Mood

“A certain percentage of people are regular nappers. If you ask these people, they’ll be aware they’re getting benefit: They’re more alert, have better moods, and they’re feeling sharper.” — Kimberly A. Cote, Ph.D. [8]

This all sounds great, right? You’re probably wondering, where could I work to get these perks.

While most employers do not currently offer the benefit of napping, there are actually quite a few large and small companies that provide the option for a “nap time”.

Companies Introducing Power Naps at Work

It’s already caught on throughout Asia and it’s picking up steam in the U.S. If you think I’m making this up, consider the list of American companies that encourage sleeping at work. Let’s start with one we all know. Heck, you probably used their service to find this article.

One of the leading tech companies of the age has energy pods that their employees can use to go to catch a mid-afternoon power nap.

This clothing line provides a nap center surrounded by a fish tank. Here employees can go to catch some much needed Zzz’s.

Huffington Post

After the company’s founder Arianna Huffington collapsed from exhaustion, she saw this as a wake-up call and wrote a book titled The Sleep Revolution . Not surprisingly, their New York City office now has two napping rooms.

According to the National Sleep Foundation, one of their studies found that a 40-minute nap improves productivity by 34%, so it is no surprise that they also have sleep pods for their employees.

The car service is another brand that has a dedicated space for employee power naps.

Employees of the social media giant really “like” the nap pods at Facebook’s main office.

Ben & Jerry’s

This brand was one of the frontrunners that allowed employees to nap on the job with a special room.

While not all companies have a dedicated room, many others allow employees to sleep at their desk, in their car, or really anywhere else they can find a place to rest their head. “Findings argue for employer policies that actively encourage napping, especially in today’s knowledge-based economy. Some companies have set up nap rooms, and Google has “nap pods” that block out light and sound.” — Robert Stickgold, PH.D. [9]

How to Optimize Office Naps

It’s possible that your boss does not permit napping, but most will allow you to have periodic breaks, and what you do during these breaks is up to you. (You still may want to run it past your boss, though. Show them this article!)

How can you maximize your daytime sleep in a work environment that doesn’t have a designated sleep space?

Find a Cool Shaded Area

Turn out the lights, close the blinds, and maybe lower the thermostat by a few degrees before drifting off.

Bring a Pillow from Home

If you are going to be napping on a regular basis, bring a small pillow from home and keep it in your desk drawer, this will at least make napping at work a little more comfortable.

Nap at or under the Desk

It may not be ideal, but either lean back in your chair, place your head on the desk or crawl underneath the desk to block out the light.

Sleep in the Break Room

This can sometimes be very noisy, but if you go at a less busy time of day it could be an ideal place to re-energize with a power sleep.

Nap in the Car

I know this didn’t work out for me, but it might for you. Sleeping in the car can be a good way to find some peace and quiet and it can be a good place to take a short nap. Make sure to crack the windows if it’s hot outside.

My final word to the employee . If you see how this could benefit your workplace, copy the link above and send it over to your boss in an email. After all, you’re only trying to help the company save some money, and you might just find that you are allowed to take that workday nap you’ve always dreamed about.

To all those employers out there . The research and evidence out there suggest that allowing your employees to get some rest benefits both parties. You not only become the awesome boss that allows power naps, but the only thing you have to lose by not trying is even more money.

Sources and References:

[1] The Do’s and Don’ts of Power Napping , Novant Health

[2] Making the Most of a Short Nap , Harvard Medical School

[3] Clocking off: The Companies Introducing Nap Time to the Workplace , The Guardian

[4] Research proves it: Naps save you money , MIT Management Sloan School

[5] A Nap Is as Good as a Pill for Lowering Blood Pressure, Research Suggests , New York Post

[6] Napping May Help with Blood Pressure Management , Science Daily

[7] A Short Daytime Nap Could Improve Memory by Fivefold, Study Finds , Medical News Today

[8] The Science of Naps , American Psychology Association

[9] Napping May Not be Such a No-No , Harvard Health Publishing

Mark Mattei

Content Writer

About Author

Mark likes to study sleep health, write content, and produce videos on his findings. When he’s not, he’s likely writing the great American screenplay, growing out his beard, or spending time with his family.

Mark is an exclusive side sleeper with broad shoulders who looks for good pressure relief for his hips and shoulders.

Combination Sleeper

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How to Power Nap

Last Updated: October 16, 2023 Approved

This article was medically reviewed by Luba Lee, FNP-BC, MS . Luba Lee, FNP-BC is a Board-Certified Family Nurse Practitioner (FNP) and educator in Tennessee with over a decade of clinical experience. Luba has certifications in Pediatric Advanced Life Support (PALS), Emergency Medicine, Advanced Cardiac Life Support (ACLS), Team Building, and Critical Care Nursing. She received her Master of Science in Nursing (MSN) from the University of Tennessee in 2006. There are 7 references cited in this article, which can be found at the bottom of the page. wikiHow marks an article as reader-approved once it receives enough positive feedback. This article has 18 testimonials from our readers, earning it our reader-approved status. This article has been viewed 2,062,976 times.

A quick power nap can help you combat drowsiness and make you more alert and productive. If you're in need of a power nap, make sure you do it right so you wake up feeling refreshed and not groggy.

Nurse Practitioner Luba Lee suggests: "Try timed meditation which has a similar effect on your body and mind as a power nap. Twenty to twenty-five minutes of laying down or sitting in meditation will improve your mood, energy, focus and decrease stress."

Things You Should Know

• Taking a brief 20-minute nap can help you feel more rested and alert when you wake up.
• Napping for longer than 30 minutes may leave you feeling groggy.
• Drinking a cup of coffee right before a power nap can actually help you feel more awake after your nap.

Finding a Good Place to Nap

• Napping at work : A survey by the National Sleep Foundation found that about 30% of people are allowed to sleep at work, and some employers even provide a place for employees to nap. [1] X Research source If your place of employment isn't nap-friendly, you can take a power-nap in your car.
• Napping on the road : If you're driving, find a rest area to park in. Don't park on the shoulder. Always turn off the car and set the emergency brake. If it's night-time, park in a well-lit area with plenty of people around and lock all of your doors.
• Napping at school : If you have the time, and are allowed to, try using the library as a good place to nap. It is usually the quietest place at school. Then after, you can also nap in your car, if you have one.

• If your napping place is too cold, have a blanket ready or a comfortable jacket you can put on. If your napping place is too warm, consider placing a fan in the room, if possible.

• If you are using your phone for a guided nap, put it on airplane mode. This will prevent phone calls or message alerts from disrupting you.

Choosing the Length of Your Nap

• A power-nap captures the benefits of the first two of the five stages in the sleep cycle. These first two stages take place in the first twenty minutes. In addition to making you feel more rested and alert, the electrical signals in your nervous system strengthen the connection between neurons involved in muscle memory, making your brain work faster and more accurately.
• It can be especially useful to take a power nap if you are trying to remember a lot of important facts, for example, for a test.

• If you have the time, and are extremely physically and mentally tired after pulling an all-nighter, for example, this nap could be useful because it gives your body enough time to repair itself.

Getting the Most Out of Your Nap

• If background noise is unavoidable, or if you suffer from tinnitus , putting on headphones with soft, relaxing music may help. You can also try using ear plugs.

• However, if it is late in the afternoon you should probably skip the caffeine, as it may make it more difficult to fall asleep at bedtime. You can also skip the caffeine if you are trying to quit caffeine .

• Keep in mind how long you need to fall asleep . If you want to take a 20 minute nap, and you usually take about five minutes to fall asleep, then you will want to set your alarm for 25 minutes. If you fall asleep very quickly, you may only need to add an extra minute or two to your desired nap time.
• If you're one of those people who has a habit of pressing the "snooze" button and going right back to sleep, put your alarm across the room, or as far away from yourself as possible if you’re in the car, so that it will not be easy to turn it off.

• You can also try putting all thoughts out of your mind. Instead, try focusing only on your breathing. This is very similar to meditating, but can also help you relax so that you can fall asleep quickly.
• Try counting down slowly from 100. If you forget what number you're on, simply start again at 100. This will help keep your mind off of thoughts that keep you awake. [6] X Research source
• You can also try one of the commercially available power nap machines or CDs that play a special soundtrack designed to induce a sleep state.

• Follow up with physical activity. Get your heart rate up a bit by doing a few jumping jacks or push-ups , you can also try a bit of jogging in place.
• Wash your face and expose yourself to bright light (e.g. sunlight), which can help you feel more awake, if you are still feeling groggy after your nap. [8] X Trustworthy Source PubMed Central Journal archive from the U.S. National Institutes of Health Go to source

Expert Q&A

• Napping till late afternoon can harm your sleeping patterns and can cause you to be sleep deprived in the morning. Thanks Helpful 41 Not Helpful 2
• Force yourself to wake up! Although it may be very relaxing you'll need to wake up and go to your task. Over power napping can mess up your sleeping pattern so make it short and snappy! Thanks Helpful 43 Not Helpful 4
• Sleeping too long during the day will keep you awake at night. Keep this in mind. Thanks Helpful 36 Not Helpful 5

• A power nap can only help to a certain extent, and cannot replace the benefits of a good night’s rest . If you're sleep-deprived, you need to manage your sleep deficit before you can realize the full benefits of power-napping. Thanks Helpful 23 Not Helpful 4
• If you have trouble sleeping at night, don't hesitate to sleep during the day, or you will end up exhausted when it matters the most. Just keep your naps short, so you don't throw off your whole sleep schedule. Thanks Helpful 22 Not Helpful 5
• While commonly found in sodas, coffee, tea, and “energy drinks,” caffeine is a powerful and potentially addictive drug. Overuse of caffeine can lead to dependence, and cause side effects such as interference with normal sleep cycles. Therefore, it is important to keep caffeine consumption to a minimum. Thanks Helpful 8 Not Helpful 1

Things You’ll Need

• A place to nap
• Alarm clock
• Caffeine (optional)
• Relaxing music (optional)
• Sleep mask (optional)
• Ear plugs (optional)

You Might Also Like

• ↑ https://fortune.com/2011/08/18/why-companies-are-cozying-up-to-napping-at-work/
• ↑ https://www.sleepfoundation.org/sleep-hygiene/napping
• ↑ http://io9.com/the-science-behind-power-naps-and-why-theyre-so-damne-1401366016
• ↑ http://www.ncbi.nlm.nih.gov/pubmed/14652086?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DiscoveryPanel.Pubmed_Discovery_RA&linkpos=5&log%24=relatedarticles&logdbfrom=pubmed
• ↑ http://www.medicaldaily.com/life-hack-sleep-4-7-8-breathing-exercise-will-supposedly-put-you-sleep-just-60-332122
• ↑ http://www.magicwandcoach.com/count-to-sleep.htm
• ↑ http://www.webmd.com/sleep-disorders/features/power-of-napping-feature?page=1

About This Article

Medical Disclaimer

The content of this article is not intended to be a substitute for professional medical advice, examination, diagnosis, or treatment. You should always contact your doctor or other qualified healthcare professional before starting, changing, or stopping any kind of health treatment.

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To take a power nap, find a quiet, dark place to sit or lie down. Once you're settled in, set an alarm for 25 minutes so you have 5 minutes to fall asleep and 20 minutes to nap. Try to relax, and avoid focusing on falling asleep, which will only keep you awake for longer. Even just resting with your eyes closed can help! When your alarm goes off, don't hit the snooze button — naps longer than 30 minutes can make you feel more groggy and tired. For tips on falling asleep quickly, like listening to soothing music, keep reading! Did this summary help you? Yes No

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How Does Batman Sleep? The Complete Guide to Batman’s Sleep Cycle

Table of Contents

How Does Batman Sleep?

Batman is one of the most popular comic book characters of all time. He has been featured in countless movies, TV shows, and video games.

But there is one aspect of Batman that has never been explored in detail: his sleep cycle.

How does Batman sleep? Does he even need to sleep?

Batman, the defender of Gotham City, (… SPOILER ALERT!!! … )leads a double life as both billionaire Bruce Wayne and the Dark Knight. With his endless list of tasks, including patrolling Gotham City, board meetings, Justice League meetings, and training sessions, it seems impossible for him to get a full night’s sleep .

In this blog post, we will take a deep dive into the world of Gotham’s Dark Knight and try to answer these questions once and for all.

Does Batman sleep at all?

Batman does sleep, but he has trained himself to manage with microsleep sessions and can compress a whole night’s sleep into three hours. He seems to follow non-Sleep Deep Rest practices. He can also function normally for three to four days without sleeping at all.

While this practice has been beneficial to him in the comics, in reality, it is considered harmful to health. Despite this, Batman’s lack of regular sleep does not seem to affect his crime-fighting abilities, as he remains vigilant and alert throughout the night.

How does Batman sleep?

Batman has trained himself to manage micro-sleep sessions, remaining unconscious for a short time. This practice is viewed as harmful to health by science, but Batman has trained his brain to deliberately go into microsleep while studying or working.

He sleeps outside in the wild – literally. But he can compress a whole night’s sleep into three hours and can continue functioning normally for three to four days without sleeping at all. Despite the unique sleep habits of the Caped Crusader, it is important to note that this type of sleep deprivation can be detrimental to one’s health.

What is the sleep cycle of Batman?

According to research, Batman’s sleep cycle involves carefully managing microsleep sessions and compressing a whole night’s sleep into three hours. To understand how this works, it’s important to understand the four stages of sleep: stage 1, stage 2, stage 3 (also known as slow-wave sleep), and REM sleep. Each stage lasts around 90 minutes, with REM sleep being the most important for physical and mental restoration.

Batman has trained himself to enter a state of hypervigilance while sleeping, allowing him to remain alert to any potential danger. He also schedules his sleep time in 90-minute periods, ensuring that he gets at least four sessions (6 hours) of sleep per day. This allows him to maintain his physical and mental abilities, despite the demands of his nocturnal crime-fighting activities.

While the concept of microsleep is viewed as dangerous in reality, Batman has used it to his advantage by training his brain to deliberately go into microsleep while studying or working. Overall, Batman’s unique sleep cycle highlights the importance of REM sleep and the adaptability of the human body to meet the demands of a non-traditional lifestyle. Resetting your sleep cycle with all-nighters is not always the best solution.

How does Batman microsleep?

Microsleep is a phenomenon where people fall unconscious for a short period of time, losing and regaining consciousness so rapidly that they are not even aware of falling asleep. While microsleeps are generally considered dangerous in real life, in the comics, Batman has learned to use microsleeps to his advantage. By training his brain to go into microsleeps while studying or working on the Bat Computer, Bruce Wayne can avoid normal sleep and maintain his alertness and vigilance.

While this practice is considered dangerous in reality, it has allowed Batman to manage his busy schedule of patrolling Gotham City, attending board meetings at Wayne Enterprises, and training with Robin. The use of microsleeps is a creative solution to the question of how Batman manages to stay awake and alert while dedicating his days and nights to fighting crime.

How many hour does Batman sleep?

According to various sources, Batman doesn’t have a consistent sleep schedule due to his crime-fighting duties. He has trained himself to compress a whole night’s sleep into three hours and can function normally for three to four days without sleeping at all.

Additionally, he is known to take micro naps to recharge his body. However, there are also instances where Alfred has forced him to get a minimum of eight hours of bedrest. Overall, it seems that Batman gets less sleep than the average person due to his nighttime activities.

What are microsleeps?

Microsleeps are brief moments of sleep that can happen unintentionally, usually due to sleep deprivation or monotony. During a microsleep, the brain waves measured by the EEG decrease significantly, but a large part of the brain remains active. Batman is known for using micro-sleep sessions to rest during his busy crime-fighting schedule. He can remain unconscious for a short time, waking up seconds later to continue his activities.

However, this practice is considered harmful to health and can have consequences such as weight gain, weakened immune system , and psychological risks even car crashes when it happens during a trip, so you should stop microsleeping to be safe.

Tips on how to help Batman get a better night’s rest

1. avoid stress.

Batman’s high-stress lifestyle can greatly affect his quality of sleep. To avoid stress and improve his rest, it’s important for him to practice relaxation techniques like meditation or deep breathing. Or he must learn how to fall asleep even when excited because of the fights.

Developing a consistent sleep routine and avoiding sleep deprivation can also aid in reducing stress and improving sleep quality. By implementing these tips, Batman can ensure he gets the rest he needs to continue fighting crime.

2. Practice relaxation techniques

As the Dark Knight, Batman needs to be alert and focused at all times. Getting quality sleep is crucial to achieving this, and there are several relaxation techniques that can help improve his sleep cycle.

• One technique is deep breathing exercises, where he can inhale deeply through his nose and exhale slowly through his mouth. This can help slow down his heart rate and calm his mind. The 478 sleep trick may not work for him all the time, though.
• Visualization techniques can also be helpful, such as imagining a peaceful scene or focusing on a specific object to clear his mind.
• Progressive muscle relaxation involves tensing and relaxing each muscle group in the body, starting from the feet and working up towards the head. This can help release tension and promote relaxation.
• Creating a comfortable sleep environment by avoiding caffeine and alcohol before bed, turning off ambient lights and sounds, and maintaining a comfortable room temperature can also improve sleep quality.

3. Take short powernaps

Batman’s ability to sustain himself and gain renewed energy from short sleep is a great advantage for his crime-fighting lifestyle. Taking short naps can benefit his sleep cycle by allowing him to have more time for his other activities while still getting the rest he needs.

It’s important to note that napping should not replace a full night’s sleep , but rather supplement it. Napping for 20-30 minutes can help boost alertness, improve mood, and increase productivity. However, napping for too long or too frequently can disrupt nighttime sleep and lead to grogginess.

4. Have a designated Batman Cave

Creating a designated Batman Cave can be a great way to improve the Dark Knight’s sleep cycle. First and foremost, the ideal location should be away from the hustle and bustle of Gotham City, preferably underground or in a secluded location.

• Lighting should be minimal, with a focus on warm, calming tones to help Batman relax.
• Decor should include comfortable bedding, pillows, and blankets, as well as any personal touches that bring Bruce Wayne comfort.
• Consider adding a sound system for playing soothing music or white noise to drown out any distractions. Remember, this space is solely for Batman’s relaxation and rejuvenation, so don’t be afraid to get creative and make it a true sanctuary for the Caped Crusader.
• He should learn how to sleep comfortably in a car – even when he is the driver.

5. New Batman Gadgets that help him get a good night’s sleep.

It’s a shame that there aren’t specific gadgets explicitly designed to help Batman get a good night’s sleep. Here’s a lighthearted list of fictional gadgets that could humorously assist Batman in achieving a restful slumber:

• Bat-Sleep Mask: A high-tech mask that blocks out all sources of light and creates a tranquil sleep environment, complete with built-in white noise and soothing music options .
• Bat-Relaxation Pod: A specialized pod equipped with ergonomic cushions, temperature control, and massage features. It cocoons Batman in a state of total relaxation, promoting deep sleep .
• Bat-Slumber Spray: A specially formulated sleep-inducing spray that Batman can use to calm his mind and drift off to sleep quickly.
• Bat-Sleep Analyzer: A device that monitors Batman’s sleep patterns, providing detailed analysis and recommendations for optimizing his sleep quality. It could suggest adjustments to his sleep environment or routines.
• Bat-Sleep Suit: A cutting-edge swaddle sleepwear ensemble made from advanced, moisture-wicking materials that regulate body temperature and provide maximum comfort during sleep.
• Bat-Dream Recorder: A device that records Batman’s dreams, allowing him to review and analyze them later. It could help him uncover hidden insights or detect potential threats in his subconscious.

Please note that these gadgets are fictional and meant for humor only.

What comic books does Batman appear in?

Batman first appeared in Detective Comics #27 in May 1939. He then appeared in Batman #1 in 1940, which introduced the Joker and Catwoman. Throughout the years, Batman has appeared in various comic book series, including Batman, Detective Comics, and The Dark Knight Returns. He has also been a part of numerous crossover events, such as Crisis on Infinite Earths and Batman: Hush.

It is interesting tha the expression get some Zzz’s is also originates from a cartoon and Zzz means sleep .

How does Batman deal with his insomnia?

Batman is known for being vigilant and operating tirelessly to protect Gotham City, which often leads to him neglecting sleep and facing bouts of insomnia. While there have been various interpretations of Batman over the years, here are a few ways in which he has dealt with his sleeplessness:

• Meditation and Mental Discipline: Batman has honed his mind through extensive training, which includes meditation techniques.
• Physical Exhaustion: Batman pushes his body to its limits through intense physical training and crime-fighting activities. By exhausting himself physically, he often finds it easier to fall asleep when he finally has the opportunity to rest.
• Brief Power Naps: When circumstances allow, Batman may take short power naps or micro naps to recharge his energy levels. These naps are usually brief and strategic, allowing him to rest just enough to regain some energy without losing focus on his mission.
• Dedication to Crime-Fighting: Batman’s unwavering dedication to protecting Gotham City often serves as a driving force that keeps him going despite his insomnia. His sense of purpose and commitment to justice motivate him to continue his vigilantism even during sleepless nights.

What are the benefits of Batman’s power naps?

Batman’s power naps, also known as microsleep sessions, allow him to sustain himself and gain renewed energy from short periods of rest. While science considers this practice harmful to health, Batman has trained himself to go into microsleep during problem-solving, boosting his mental acuity in bursts.

These power naps help him manage the rigors of his double life and maintain his legacy as the World’s Greatest Detective without compromising his crime-fighting abilities.

How does Batman’s alter ego, Bruce Wayne, affect his sleep?

Bruce Wayne’s alter ego significantly affects Batman’s sleep cycle. As an ordinary human with no superpowers, sleep is a necessity for him. However, with endless tasks like patrolling Gotham City, attending Wayne Enterprises board meetings, and training sessions, it’s impossible for Bruce to get the recommended eight hours of sleep.

To cope, Bruce has learned to manage micro-sleep sessions, remaining unconscious for a short time. The rigors of Bruce’s double life take a physical toll on his body, and he often takes small naps on the job, either as Bruce or the Dark Knight. Think of it like a power nap for a busy executive, except Batman’s power nap is a few seconds long.

Does batman sleep upside down?

In the movies, such as Tim Burton’s Batman and Christopher Nolan’s Batman Begins, Bruce Wayne can be seen sleeping in a giant bed or even hanging upside down like a bat. However, according to the comics, neither of these positions are Batman’s preferred method of sleeping. Instead, he has learned to engage in “micro-naps” or “microsleep.” So, the answer is no, Batman does not sleep upside down.

Read more about another superhero Odin from the Norse mythology who has a famous sleep cycle: the Odinsleep .

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Stephen Colbert Jokes Trump Took a 'White Power Nap' in Court | Video

D onald Trump fell asleep in court on Tuesday, the second day in a row he's nodded off during his criminal trial in New York. Naturally, "The Late Show" host Stephen Colbert was delighted about this embarrassing spectacle, and he proposed an interesting theory for why it might be happening.

But first, he coined an excellent pun about the nap Trump took on Monday. "Yesterday, Trump fell asleep. During the proceedings. He took a little white power nap," Colbert said. "But today he was sharp, focused and he fell asleep again."

The CBS host then dropped his theory as to why Trump keeps sleeping in court, adding, "And in a totally unrelated story, there's a national Adderall shortage. No relation."

"Trump must have snoozed for a while because the court sketch artist had time to draw him," Colbert said as a screenshot of the actual court sketch appeared. "Well, I think we found the new mascot for Celestial Seasonings: Sleepy crime tea."

Later in the monologue, Colbert came up with a novel way for Trump to end up with a favorable jury. He got there by noting that among the ways Trump tried to con his way out of having to attend court every day, he asked to attend his son, Baron Trump's high school graduation.

Colbert noted that the presiding judge said, "'It really depends on if we are on time and where we are in the trial.' But he has to go to the graduation. He already wrote the speech."

Then Colbert did his impression of Trump giving a speech, saying, "'Mr. valedictorian, you say the future is bright, but the truth is our country is dying. There is no future and Valerie is not the true prom queen. The election was stolen from me. Stop the steal crooked Mallory.'"

"Now to be clear, Judge Merchan never said Trump couldn't attend his son's graduation, but that did not stop Trump from pretending," Colbert said, quoting the unhinged message Trump posted on Truth Social claiming this was the case. And this brought him to the jury situation.

One of the things Trump said in that message was he "will likely not be allowed to attend his graduation ceremony."

"I don't blame him for wanting someone else to do that," Colbert joked, meaning the judge. Imitating Trump again, he said, "Son, you know how right after you were born, I cheated on your mom? I banged a porn star? Oh, you didn't know that. You want to be on my jury?"

Watch the whole monologue, above.

The post Stephen Colbert Jokes Trump Took a 'White Power Nap' in Court | Video appeared first on TheWrap .

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NPR defends its journalism after senior editor says it has lost the public's trust

David Folkenflik

NPR is defending its journalism and integrity after a senior editor wrote an essay accusing it of losing the public's trust. Saul Loeb/AFP via Getty Images hide caption

NPR is defending its journalism and integrity after a senior editor wrote an essay accusing it of losing the public's trust.

NPR's top news executive defended its journalism and its commitment to reflecting a diverse array of views on Tuesday after a senior NPR editor wrote a broad critique of how the network has covered some of the most important stories of the age.

"An open-minded spirit no longer exists within NPR, and now, predictably, we don't have an audience that reflects America," writes Uri Berliner.

A strategic emphasis on diversity and inclusion on the basis of race, ethnicity and sexual orientation, promoted by NPR's former CEO, John Lansing, has fed "the absence of viewpoint diversity," Berliner writes.

NPR's chief news executive, Edith Chapin, wrote in a memo to staff Tuesday afternoon that she and the news leadership team strongly reject Berliner's assessment.

"We're proud to stand behind the exceptional work that our desks and shows do to cover a wide range of challenging stories," she wrote. "We believe that inclusion — among our staff, with our sourcing, and in our overall coverage — is critical to telling the nuanced stories of this country and our world."

NPR names tech executive Katherine Maher to lead in turbulent era

She added, "None of our work is above scrutiny or critique. We must have vigorous discussions in the newsroom about how we serve the public as a whole."

A spokesperson for NPR said Chapin, who also serves as the network's chief content officer, would have no further comment.

Praised by NPR's critics

Berliner is a senior editor on NPR's Business Desk. (Disclosure: I, too, am part of the Business Desk, and Berliner has edited many of my past stories. He did not see any version of this article or participate in its preparation before it was posted publicly.)

Berliner's essay , titled "I've Been at NPR for 25 years. Here's How We Lost America's Trust," was published by The Free Press, a website that has welcomed journalists who have concluded that mainstream news outlets have become reflexively liberal.

Berliner writes that as a Subaru-driving, Sarah Lawrence College graduate who "was raised by a lesbian peace activist mother ," he fits the mold of a loyal NPR fan.

Yet Berliner says NPR's news coverage has fallen short on some of the most controversial stories of recent years, from the question of whether former President Donald Trump colluded with Russia in the 2016 election, to the origins of the virus that causes COVID-19, to the significance and provenance of emails leaked from a laptop owned by Hunter Biden weeks before the 2020 election. In addition, he blasted NPR's coverage of the Israel-Hamas conflict.

On each of these stories, Berliner asserts, NPR has suffered from groupthink due to too little diversity of viewpoints in the newsroom.

The essay ricocheted Tuesday around conservative media , with some labeling Berliner a whistleblower . Others picked it up on social media, including Elon Musk, who has lambasted NPR for leaving his social media site, X. (Musk emailed another NPR reporter a link to Berliner's article with a gibe that the reporter was a "quisling" — a World War II reference to someone who collaborates with the enemy.)

When asked for further comment late Tuesday, Berliner declined, saying the essay spoke for itself.

The arguments he raises — and counters — have percolated across U.S. newsrooms in recent years. The #MeToo sexual harassment scandals of 2016 and 2017 forced newsrooms to listen to and heed more junior colleagues. The social justice movement prompted by the killing of George Floyd in 2020 inspired a reckoning in many places. Newsroom leaders often appeared to stand on shaky ground.

Leaders at many newsrooms, including top editors at The New York Times and the Los Angeles Times , lost their jobs. Legendary Washington Post Executive Editor Martin Baron wrote in his memoir that he feared his bonds with the staff were "frayed beyond repair," especially over the degree of self-expression his journalists expected to exert on social media, before he decided to step down in early 2021.

Since then, Baron and others — including leaders of some of these newsrooms — have suggested that the pendulum has swung too far.

Author Interviews

Legendary editor marty baron describes his 'collision of power' with trump and bezos.

New York Times publisher A.G. Sulzberger warned last year against journalists embracing a stance of what he calls "one-side-ism": "where journalists are demonstrating that they're on the side of the righteous."

"I really think that that can create blind spots and echo chambers," he said.

Internal arguments at The Times over the strength of its reporting on accusations that Hamas engaged in sexual assaults as part of a strategy for its Oct. 7 attack on Israel erupted publicly . The paper conducted an investigation to determine the source of a leak over a planned episode of the paper's podcast The Daily on the subject, which months later has not been released. The newsroom guild accused the paper of "targeted interrogation" of journalists of Middle Eastern descent.

Heated pushback in NPR's newsroom

Given Berliner's account of private conversations, several NPR journalists question whether they can now trust him with unguarded assessments about stories in real time. Others express frustration that he had not sought out comment in advance of publication. Berliner acknowledged to me that for this story, he did not seek NPR's approval to publish the piece, nor did he give the network advance notice.

Some of Berliner's NPR colleagues are responding heatedly. Fernando Alfonso, a senior supervising editor for digital news, wrote that he wholeheartedly rejected Berliner's critique of the coverage of the Israel-Hamas conflict, for which NPR's journalists, like their peers, periodically put themselves at risk.

Alfonso also took issue with Berliner's concern over the focus on diversity at NPR.

"As a person of color who has often worked in newsrooms with little to no people who look like me, the efforts NPR has made to diversify its workforce and its sources are unique and appropriate given the news industry's long-standing lack of diversity," Alfonso says. "These efforts should be celebrated and not denigrated as Uri has done."

After this story was first published, Berliner contested Alfonso's characterization, saying his criticism of NPR is about the lack of diversity of viewpoints, not its diversity itself.

"I never criticized NPR's priority of achieving a more diverse workforce in terms of race, ethnicity and sexual orientation. I have not 'denigrated' NPR's newsroom diversity goals," Berliner said. "That's wrong."

Questions of diversity

Under former CEO John Lansing, NPR made increasing diversity, both of its staff and its audience, its "North Star" mission. Berliner says in the essay that NPR failed to consider broader diversity of viewpoint, noting, "In D.C., where NPR is headquartered and many of us live, I found 87 registered Democrats working in editorial positions and zero Republicans."

Berliner cited audience estimates that suggested a concurrent falloff in listening by Republicans. (The number of people listening to NPR broadcasts and terrestrial radio broadly has declined since the start of the pandemic.)

Former NPR vice president for news and ombudsman Jeffrey Dvorkin tweeted , "I know Uri. He's not wrong."

Others questioned Berliner's logic. "This probably gets causality somewhat backward," tweeted Semafor Washington editor Jordan Weissmann . "I'd guess that a lot of NPR listeners who voted for [Mitt] Romney have changed how they identify politically."

Similarly, Nieman Lab founder Joshua Benton suggested the rise of Trump alienated many NPR-appreciating Republicans from the GOP.

In recent years, NPR has greatly enhanced the percentage of people of color in its workforce and its executive ranks. Four out of 10 staffers are people of color; nearly half of NPR's leadership team identifies as Black, Asian or Latino.

"The philosophy is: Do you want to serve all of America and make sure it sounds like all of America, or not?" Lansing, who stepped down last month, says in response to Berliner's piece. "I'd welcome the argument against that."

"On radio, we were really lagging in our representation of an audience that makes us look like what America looks like today," Lansing says. The U.S. looks and sounds a lot different than it did in 1971, when NPR's first show was broadcast, Lansing says.

A network spokesperson says new NPR CEO Katherine Maher supports Chapin and her response to Berliner's critique.

The spokesperson says that Maher "believes that it's a healthy thing for a public service newsroom to engage in rigorous consideration of the needs of our audiences, including where we serve our mission well and where we can serve it better."

Disclosure: This story was reported and written by NPR Media Correspondent David Folkenflik and edited by Deputy Business Editor Emily Kopp and Managing Editor Gerry Holmes. Under NPR's protocol for reporting on itself, no NPR corporate official or news executive reviewed this story before it was posted publicly.

Three Rhode Island power players just launched a political nonprofit

The group’s goal is to “influence policy makers and constituents to work for progressive change in housing, education, labor, and health care, particularly women’s health care,” according to incorporation papers.

We’re still a few months away from Rhode Island’s elections taking center stage, but three of the best-known insiders in the state have just launched a new nonprofit “social welfare” organization that they believe will play a big role in local politics for years to come.

Kate Coyne-McCoy, a former executive director of the state Democratic Party, George Zainyeh, who was chief of staff to former governor Lincoln Chafee and is now one of the most influential lobbyists on Smith Hill, and Patti Doyle, a top communications pro for just about everyone, formed Better RI NOW on April 8.

The group’s plans are still vague, but its goal is to “influence policy makers and constituents to work for progressive change in housing, education, labor, and health care, particularly women’s health care,” according to incorporation papers.

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Asked to expand on the group’s goals, Doyle said the group plans to raise money, but won’t directly endorse candidates for office. She said “we can let voters know which candidates stand for issues important to them.”

”The three of us have been active in public policy for a while, we witness the ongoing national dialogue, and just want to be additive to a local conversation on a variety of key issues,” Doyle said.

Stepping back: Coyne-McCoy, Zainyeh, Doyle aren’t necessarily household names to the average Rhode Islander, but they’re a powerful trifecta in political circles. Doyle said the group plans to focus on the congressional delegation and statewide offices.

US Senator Sheldon Whitehouse and US Representatives Seth Magaziner and Gabe Amo are all on the ballot this year, although all three are heavy favorites to be reelected (especially in a presidential election year). It’s more intriguing to think about the role Better RI NOW might play in 2026 in Rhode Island.

This story first appeared in Rhode Map, our free newsletter about Rhode Island that also contains information about local events, links to interesting stories, and more. If you’d like to receive it via e-mail Monday through Friday, you can sign up here.

Dan McGowan can be reached at [email protected] . Follow him @danmcgowan .

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The Language of Gender Identity

More from our inbox:, power over principle in the g.o.p., upgrading our electric grid, shakespeare’s insights, still relevant today.

To the Editor:

Re “ The Problem With Saying ‘Sex Assigned at Birth, ’” by Alex Byrne and Carole K. Hooven (Opinion guest essay, nytimes.com, April 3):

Mr. Byrne and Ms. Hooven argue that use of “assigned sex” terminology “creates doubt about a biological fact when there shouldn’t be any.” But sex characteristics are not “a biological fact”; they are rather a series of facts — anatomical, hormonal and genetic — that are not always in alignment.

The term “sex assignment” derives from the medical literature of the 1940s and 1950s, in which physicians grappled with what was then called “hermaphroditism” and is now called “intersex” or “D.S.D.,” for disorders or differences of sex development.

To conclude that the words “assigned at birth” are needless is to deny the complexity of biological sex and to erase both the history of intersex conditions and the embodied reality of the people who are born and live with them.

Barbara M. Chubak New York The writer is an associate professor of urology at the Icahn School of Medicine at Mount Sinai.

Transgender people like me do not exist as a topic of rational debate, something to be tossed around in discourse; we are people, and our lives exist far beyond your philosophizing. Articles like this are not only unnecessary, but they are also harmful, patronizing and dehumanizing.

The phrase “sex assigned at birth” is causing no one any harm, and it is not meant to replace “sex.” We are not advocating the end of “male” and “female.”

“Sex assigned at birth” is simply meant to convey the following notion: This individual was born as one sex, but their current body and/or lived experiences may contradict that. It allows trans people the very medical clarity this article claims to strive for. If I, a trans man far into his medical transition, were to walk into a doctor’s office and claim to simply be “female,” utter confusion could follow.

But we should not have to defend ourselves under the guise of rational discourse. We have bigger issues. In Texas, my parents would be possibly liable for child abuse for allowing me to transition as a teenager — so stop treating us as if we do not know what we are talking about.

When people tell you the language that makes them the most comfortable, you use it and move on. You may believe sex to be black and white, as it may be the most convenient reality for you to live in, but for many of us, our bodies are the gray areas.

Max Greenhill New York

I fully agree with this essay: Biological sex is accurately recorded at birth; it is not arbitrarily “assigned.”

The reason activists are pushing the sex-assigned-at-birth terminology is not simply that they want more empathy and inclusiveness for trans persons, but that they want the public to believe that one’s birth sex was, as the authors say, an educated guess at best. If the public accepts that idea, they will be more agreeable to the idea that one’s misassigned sex needs to be corrected later when the individual is old enough to determine their “true, authentic self.”

Most adults don’t care what gender someone declares, but biological sex is a scientific fact. The range of “genders” now being proclaimed is making the whole concept of gender meaningless. Every behavior, feeling, mood, attribute, sexual orientation or social statement does not constitute a gender.

Mark Godburn Norfolk, Conn.

The problem is not that we are confusing the male/female binary; the problem is that the human gender story is bigger than a simple binary, and our language does not reflect that, but it should.

Intersex people exist and have always existed. People whose gender expression doesn’t match their biological presentation exist and have always existed. The authors are correct that language is powerful, but in this case they have the power dynamic exactly backward.

When we adhere to strict binary language, we are asking gender-abundant people to amputate whole parts of themselves. We need to allow people to flourish in the language that fits them.

As my 9-year-old recently explained to my 6-year-old, “You don’t really know what gender a baby is when it’s born, because you know their parts, but you don’t know their heart.”

Meghan Lin St. Paul, Minn.

Thank you, thank you, thank you for publishing this guest essay by Alex Byrne and Carole K. Hooven. In a society inundated with well-meaning absurdities such as “sex assigned at birth” and “pregnant people,” this message desperately needs to be broadcast, received and acted upon.

Mark Featherstone Alameda, Calif.

Re “ Sununu Says Trump ‘Contributed’ to Insurrection, but Still Has His Support ” (news article, nytimes.com, April 14):

Gov. Chris Sununu of New Hampshire now says he will support Donald Trump for president, even as he concedes that Mr. Trump “absolutely contributed” to an attempted insurrection on Jan. 6. Like many of his fellow Republicans, Mr. Sununu has chosen power over principle.

Ethics don’t flash on and off like neon lights. Integrity cannot be situational. And character isn’t a chameleon that shifts to secure political advantage. History will record all the elected officials who embraced Mr. Trump’s mendacity while looking away from the democratic principles they swore an oath to uphold.

Welcome to the club, Governor Sununu.

Maryellen Donnellan Falls Church, Va.

Re “ The U.S. Urgently Needs a Bigger Grid. Scientists Have a Faster Solution ” (Business, April 10):

The nation’s current power lines that were built in the 1950s and 1960s have a 50-year life expectancy, meaning that they have surpassed their intended life span. As the U.S. evaluates how to meet new electric demand, the materials in the grid must not just be replaced, but also efficiently planned and upgraded.

To lower energy costs and improve reliable access to electricity, we should use new technologies that allow more power to be transported across the same size transmission towers that are currently in use. Further, the same amount of power could be transported across smaller, low-impact towers, which could reduce siting and permitting obstacles — thus saving time and money.

Significant transmission capacity is required to meet rising demands on the electrical system, withstand frequent extreme weather events and balance a changing resource mix. Deploying improved technologies in constructing a nationwide transmission grid is key to meeting these needs — because America needs a modern grid now more than ever.

Christina Hayes Washington The writer is the executive director of Americans for a Clean Energy Grid.

With “ O.J. and the Monster Jealousy ” (column, April 14) and “ Trump’s Insatiable Bloodlust ” (column, April 7), Maureen Dowd evokes two of Shakespeare’s greatest characters — Othello and Macbeth — to demonstrate that the playwright’s insights remain as perceptive and significant today as they were more than 400 years ago.

As his friend and fellow dramatist Ben Jonson wrote of Shakespeare, “He was not of an age but for all time!”

Brad Bradford Upper Arlington, Ohio