Suppression of sleepiness in drivers: combination of caffeine with a short nap

Psychophysiology. 1997 Nov;34(6):721-5. doi: 10.1111/j.1469-8986.1997.tb02148.x.


Previous research has shown that caffeine and a < 15-min nap effectively and separately reduce sleepiness in drivers for 1 hr. In the present study, we examined in 12 sleepy individuals the treatments combined, taken during a 30-min break, prior to a longer (2 hr) continuous monotonous afternoon drive in a car simulator. Nonnap comparisons were 200 mg caffeine only and placebo. For placebo, driving incidents, subjective and electroencephalographic measures of sleepiness all reflected a mid-afternoon peak. This peak was significantly reduced by caffeine and eliminated by the combined treatment, which reduced incidents to 9% of placebo levels versus 34% of placebo levels for caffeine alone. Naps comprising "nonsleep dozing" were still effective.

Publication types

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

MeSH terms

  • Adult
  • Automobile Driving*
  • Caffeine / pharmacology*
  • Central Nervous System Stimulants / pharmacology*
  • Electroencephalography / drug effects
  • Female
  • Humans
  • Male
  • Sleep / drug effects
  • Sleep / physiology*
  • Sleep Stages / drug effects*


  • Central Nervous System Stimulants
  • Caffeine