Inducing more sleep on school nights reduces sedentary behavior without affecting physical activity in short-sleeping adolescents.

Objectives/background: Short sleep duration during adolescence is associated with increased dietary intake and greater risk for overweight/obesity. However, findings are mixed on the relationship between sleep and physical activity (PA) during the school year, when short sleep duration is most common. Furthermore, there is concern that increasing sleep duration may interfere with opportunities for PA, yet this has not been directly tested. This study examined the impact of an at-home experimental sleep extension protocol on PA during the school year among short-sleeping adolescents.

Participants/methods: Participants included 18 adolescents (67% female, 78% white) who reported regularly sleeping between 5-7 h on school nights. Adolescents completed a five-week, at-home sleep manipulation protocol with an initial baseline week followed in a randomized, counterbalanced order by two experimental conditions, each lasting two weeks. During prescribed habitual sleep (HAB), bedtimes and rise times were set to match the baseline sleep pattern, and during sleep extension (EXT), adolescents were instructed to increase time in bed on school nights by 1.5 h per night relative to baseline. Wrist-mounted actigraphy was employed to monitor sleep and waist-mounted accelerometers were used to measure daytime PA.

Results: Adolescents slept for an average duration of 71 min longer on school nights during EXT than during HAB (p < 0.001). During HAB, adolescents spent more time in sedentary behavior (p = 0.002) than during EXT, but there were no cross-condition differences in light activity (p = 0.184) or moderate-to-vigorous PA (p = 0.102).

Conclusions: Extending sleep duration on school nights in short-sleeping adolescents reduces time spent in sedentary behavior, without having a negative impact on health-promoting moderate-to-vigorous PA.