Daytime sleepiness and sleep-wake schedules.

Abstract

The present study assessed the differential effects of three manipulations of the sleep-wake schedules of college students on their levels of daytime sleepiness as measured by daily subjective ratings. The study was longitudinal and prospective. Following a baseline period (12 days), three experimental conditions were introduced. In the first group students were asked to sleep at least 7.5 hours at night and to avoid taking naps. In the second group, students were asked in addition to follow a regular sleep wake schedule. In the third group students were asked to sleep at least 7 hours at night and to take daily naps. The experimental phase lasted four weeks and overall, compliance was good. A follow up phase (one week) began five weeks past the termination of the experimental phase. The findings indicate that when nocturnal sleep is not deprived, regularization of the sleep-wake schedules lead to reduced sleepiness and improved psychological and cognitive functioning. Subjects in the regular schedule condition experienced greater and longer lasting improvements in their alertness compared with subjects in the other two groups combined. Napping was not found to produce any change in daytime sleepiness, but subjects who had greater increases in the regularity of nap frequency experienced greater decrease in daytime sleepiness. Subjects with evening tendencies benefited most from regularizing their sleep schedules whereas subjects with morning tendencies benefited most from taking naps.