Influence of mid-afternoon nap duration and sleep parameters on memory encoding, mood, processing speed, and vigilance.
Level 2 - randomized trial
Individual randomized crossover trial
PubMed 36775965 · doi:10.1093/sleep/zsad025
What was done
Thirty-two young adults with habitual short sleep completed four experimental conditions in randomized order: wake control, 10-minute nap, 30-minute nap, and 60-minute nap, verified by polysomnography. A 10-minute test battery measuring mood, subjective sleepiness, speed of processing, and vigilance was administered at baseline and at 5, 30, 60, and 240 minutes post-nap. Participants encoded pictures 90 minutes post-nap and completed a recognition test 210 minutes later to evaluate memory encoding and sleep macrostructure effects.
What was found
Naps between 10 and 60 minutes elevated positive mood and reduced self-reported sleepiness for up to 240 minutes post-awakening. Only the 30-minute nap condition significantly improved subsequent memory encoding compared to the wake condition. Vigilance improvements were described as moderate, while speed of processing showed no benefit. Sleep inertia was detected after 30-minute and 60-minute naps but resolved within 30 minutes. No significant associations between sleep macrostructure and memory improvements were found. The abstract reports no exact numerical values, test statistics, or effect sizes.
Why it matters
This study indicates that mid-afternoon naps provide sustained alertness and mood benefits lasting at least 4 hours, identifying a 30-minute duration as offering the best balance of cognitive enhancement, practical duration, and manageable sleep inertia.
Limits
The sample was small (32 participants) and restricted to healthy young adults with habitual short sleep, limiting generalizability to older demographics or well-rested individuals. The abstract omits quantitative point estimates, variance, and exact statistical values.
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- supports Taking a nap longer than 20 minutes increases sleep inertia upon waking.