Changes in Cognition and Mood Due to Sleep Inertia After 30-hour Sleep Deprivation

Abstract

Objective: To discuss the changes in objective cognition and subjective mood due to sleep inertia (SI) during a siesta after 30hour sleep deprivation (SD). Methods: This study was designed to investigate in eight healthy young males: 1) sleep structure during sleep periods using polysomnographic(PSG)monitoring and 2) self-ratings of alertness and reaction scores in cognitive tasks repeatedly assessed after sleep episodes. The battery of tests included a verbal working memory test, spatial working memory test, logical thinking test, and visual analog scale (VAS) tests. Four tests were randomized and administered at an interval of 30 minutes between two test batteries. There were repeated measures under nap and nonnap conditions at noon after 30-hour SD. Results: Sleep electroencephalography(EEG)showed characteristics of slow-wave sleep (SWS) when participants were awakened from a one-hour nap after 30-hour SD and deep sleep waves (especially stage III) were the main components. Results by analysis of variance (ANOVA) with repeated measures indicated that dissipation of SI had influences on cognition and subjective mood. Cognitive performance and positive mood increased under the nap condition while they decreased or remained unchanged under the nonnap condition. Conclusions: This study suggests that a nap improves positive moods factors but it does not improve objective cognition.