Dissecting circadian and homeostatic processes in adolescents: An actigraphic study

The present work used actigraphy to ecologically analyze the roles of circadian and homeostatic processes during the wake-sleep and sleep-wake transitions in adolescents. Four hundred and forty-three adolescents (15.6 ± 1.2 mean age; 45.1 % females) were enrolled in the research and wore an actigraph on the non-dominant wrist for at least three nights. We extracted the minute-by-minute motor activity counts across the wake-sleep transition to depict the motor wake inertia as modulated by the total of the previous wake hour (homeostatic process) or by the time of day of the bedtime (circadian process). The same was done for the sleep-wake transition to analyze whether motor sleep inertia is modulated primarily by the previous total sleep time or by the time of awakening. We performed the Functional Linear Modelling statistical framework in addition to the usual parametric statistics. Overall, results indicate a more substantial role of the homeostatic process in comparison to the circadian process during the wake-sleep transition, while results are less clear for the sleep-wake transition. The findings underscore the importance of ecologically studying the transition phases between wakefulness and sleep, as well as sleep and wakefulness, through actigraphy. To formulate new guidelines aimed at enhancing sleep quality during adolescence, further research is essential. For instance, it would be beneficial to explore how this pattern of outcomes may differ across the lifespan.