The alerting effects of caffeine, bright light and face washing after a short daytime nap.
OBJECTIVE
The present study examined whether the combination of a short daytime nap with caffeine, bright light and face washing was effective against mid-afternoon sleepiness.


METHODS
Ten young healthy adults participated in 5 experimental conditions; those experiments were-Nap only: taking a 20 min nap; Caffeine+Nap: taking 200 mg of caffeine followed by a nap; Nap+Bright-light: being exposed to 2000 lx of bright light for 1 min immediately after napping; Nap+Face-washing: washing their faces immediately after napping; and No-Nap: taking a rest without sleep. These naps were taken at 12:40 hours. The subjects engaged in computer tasks for 15 min before napping and for 1 h after napping.


RESULTS
Caffeine+Nap was the most effective for subjective sleepiness and performance level; its effects lasted throughout 1 h after napping. Nap+Bright-light was comparable with Caffeine+Nap, except for performance level. Nap+Face-washing showed mild and transient effects, however, it suppressed subjective sleepiness immediately after napping.


CONCLUSIONS
The effects of a short nap against mid-afternoon sleepiness could be enhanced by combining caffeine intake, exposure to bright light, or face washing.


CONCLUSIONS
The present study would provide effective countermeasures against mid-afternoon sleepiness and sleepiness related accidents.
Hayashi
Mitsuo
M
Department of Behavioral Sciences, Faculty of Integrated Arts and Sciences, Hiroshima University, 1-7-1, Kagamiyama, Higashi-Hiroshima 739-8521, Japan. mhayasi@hiroshima-u.ac.jp
Masuda
Akiko
A
Hori
Tadao
T
D000328:Adult; D002110:Caffeine / Q000008:administration & dosage*; D000697:Central Nervous System Stimulants / Q000008:administration & dosage*; D004569:Electroencephalography; D004576:Electromyography; D004585:Electrooculography; D005071:Evoked Potentials; D005145:Face; D005260:Female; D006801:Humans; D008029:Lighting; D008297:Male; D009043:Motor Activity; D012890:Sleep / Q000502:physiology; D014851:Wakefulness / Q000187:drug effects / Q000502:physiology*
D000697:Central Nervous System Stimulants; D002110:Caffeine