The alerting effects of caffeine, bright light and face washing after a short daytime nap

Clin Neurophysiol. 2003 Dec;114(12):2268-78. doi: 10.1016/s1388-2457(03)00255-4.


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.

Significance: The present study would provide effective countermeasures against mid-afternoon sleepiness and sleepiness related accidents.

Publication types

  • Clinical Trial
  • Controlled Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Caffeine / administration & dosage*
  • Central Nervous System Stimulants / administration & dosage*
  • Electroencephalography
  • Electromyography
  • Electrooculography
  • Evoked Potentials
  • Face
  • Female
  • Humans
  • Lighting*
  • Male
  • Motor Activity*
  • Sleep / physiology
  • Wakefulness / drug effects
  • Wakefulness / physiology*


  • Central Nervous System Stimulants
  • Caffeine