Recuperative power of a short daytime nap with or without stage 2 sleep.
OBJECTIVE
The recuperative effect of a nap of less than 30 minutes has been confirmed. Such naps consist mainly of stages 1 and 2 sleep. The present study examined whether sleep stage 1 or 2 contributed to the recuperative effect of a short nap.


METHODS
Repeated-measurement within-subject design. After sleep was restricted to 1.5 hours less than their usual nocturnal sleep, participants took a rest (No-nap condition) or a nap at 2:00 PM. In the nap condition, they were awakened after 5 minutes of stage 1 sleep (S1-nap condition) or 3 minutes after stage 2 sleep appeared (S2-nap condition).


METHODS
University sleep laboratory.


METHODS
Ten healthy university students (aged 19 to 24 years).


METHODS
Subjective mood, performance on visual detection and symbol-digit substitution tasks, and the number of slow eye movements during a performance task were measured before and after the nap or rest.


RESULTS
In the No-nap condition, subjective mood and performance deteriorated, and Slow eye movements increased during mid-afternoon, suggesting that the post-lunch dip occurred. In contrast, subjective alertness and performance improved and slow eye movements rarely occurred in the S2-nap condition. Although subjective sleepiness and fatigue improved, performance deteriorated and slow eye movements increased in the S1-nap condition.


CONCLUSIONS
A daytime short nap containing 3 minutes of stage 2 sleep has recuperative effects, whereas these effects are limited following only stage 1 sleep.
Hayashi
Mitsuo
M
Department of Behavioral Sciences, Faculty of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima, Japan. mhayasi@hiroshima-u.ac.jp
Motoyoshi
Naoko
N
Hori
Tadao
T
D000328:Adult; D006970:Disorders of Excessive Somnolence / Q000517:prevention & control; D004569:Electroencephalography; D005133:Eye Movements; D005221:Fatigue / Q000517:prevention & control; D005260:Female; D006801:Humans; D008297:Male; D012146:Rest; D017603:Signal Detection, Psychological; D012890:Sleep / Q000502:physiology*; D012894:Sleep Stages / Q000502:physiology*; D014796:Visual Perception