Circadian preference, nighttime sleep and daytime functioning in young adulthood

The aim of this study was to investigate whether evening circadian preference, as measured by the Horne and Ostberg questionnaire, is associated with disrupted nighttime sleep, poorer daytime functioning, and substance/drug use in young adults. The sample was comprised of 1271 first-year university students; the mean age was 18.85 +/- 1.45 years, and 35.45% were men. The study was cross-sectional, and the participants completed self-reported, anonymous questionnaires provided during an in-class survey. Multivariate logistic regression models showed that evening types (E-types) were characterized by having difficulties initiating sleep, following irregular sleep-wake patterns, and having a higher perceived sleep debt. Moreover, missing classes due to oversleeping, reporting excessive daytime sleepiness, and using more tobacco and alcohol were the daytime variables most associated with having an evening circadian preference. These results suggest that circadian preference might be related not only to different sleep-wake schedules but also to different lifestyles, a fact that is discussed in relation to recent models of circadian regulation of the sleep-wake cycle. Future studies will be necessary to better clarify the complex relationship between circadian preference, disturbed sleep, daytime sleepiness and substance/drug use.