Association of Delaying School Start Time With Sleep–Wake Behaviors Among Adolescents

Purpose: Few adolescents spend enough time asleep on school nights. This problem could be addressed by delaying high school start times, but does this translate to reduced prevalence of sleep–wake problems like awakening too early or feeling sleepy during the day? Methods: The START study (n = 2,414) followed a cohort of students from five Minnesota high schools to evaluate impacts of school start time delays. Participants were enrolled in ninth grade (Baseline) when all schools started early (7:30 or 7:45 A.M.). At Follow-Up 1 (10th grade) and Follow-Up 2 (11th grade), two schools had delayed their start times by 50 and 65 minutes while three comparison schools started at 7:30 A.M. Six sleep–wake behaviors were assessed at all three time points via survey. Generalized estimating equation models were used to investigate changes in sleep–wake problems between policy change and comparison schools. Results: The prevalence of sleep–wake problems at Baseline ranged from 11% for being late to class due to oversleeping to 48% for needing to be told to wake multiple times in the morning. Compared to students from comparison schools, students at policy change schools reported smaller increases in the prevalence of feeling sleepy daily and oversleeping and being late to class between 9th and 11th grade. After implementation of the delayed start, awakening too early was more common among students at policy change schools compared to the comparison schools. Conclusions: This longitudinal study provides evidence that delaying high school start times reduces daytime sleepiness and school tardiness.