Importance: Sleep is a resource that has been associated with health and well-being; however, sleep insufficiency is common among adolescents. Objective: To examine how delaying school start time is associated with objectively assessed sleep duration, timing, and quality in a cohort of adolescents. Design, Setting, and Participants: This observational cohort study took advantage of district-initiated modifications in the starting times of 5 public high schools in the metropolitan area of Minneapolis and St Paul, Minnesota. A total of 455 students were followed up from grade 9 (May 3 to June 3, 2016) through grade 11 (March 15 to May 21, 2018). Data were analyzed from February 1 to July 24, 2019. Exposures: All 5 participating schools started early (7:30 am or 7:45 am) at baseline (2016). At follow-up 1 (2017) and continuing through follow-up 2 (2018), 2 schools delayed their start times by 50 and 65 minutes, whereas 3 comparison schools started at 7:30 am throughout the observation period. Main Outcomes and Measures: Wrist actigraphy was used to derive indices of sleep duration, timing, and quality. With a difference-in-difference design, linear mixed-effects models were used to estimate differences in changes in sleep time between delayed-start and comparison schools. Results: A total of 455 students were included in the analysis (among those identifying sex, 225 girls [49.5%] and 219 boys [48.1%]; mean [SD] age at baseline, 15.2 [0.3] years). Relative to the change observed in the comparison schools, students who attended delayed-start schools had an additional mean 41 (95% CI, 25-57) objectively measured minutes of night sleep at follow-up 1 and 43 (95% CI, 25-61) at follow-up 2. Delayed start times were not associated with falling asleep later on school nights at follow-ups, and students attending these schools had a mean difference-in-differences change in weekend night sleep of -24 (95% CI, -51 to 2) minutes from baseline to follow-up 1 and -34 (95% CI, -65 to -3) minutes from baseline to follow-up 2, relative to comparison school participants. Differences in differences for school night sleep onset, weekend sleep onset latency, sleep midpoints, sleep efficiency, and the sleep fragmentation index between the 2 conditions were minimal. Conclusions and Relevance: This study found that delaying high school start times could extend adolescent school night sleep duration and lessen their need for catch-up sleep on weekends. These findings suggest that later start times could be a durable strategy for addressing population-wide adolescent sleep deficits..
Bibliographical noteFunding Information:
Funding/Support: This study was supported by grant R01 HD088176 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) of the NIH. The authors also gratefully acknowledge support from the Minnesota Population Center (grant P2C HD041023), which is funded through a grant from the NICHD.
reported receiving grants from the National Institutes of Health (NIH) during the conduct of the study and grants from the Department of Education and funding from ClearWay Minnesota outside the submitted work. Dr Berger reported receiving grants from the NIH during the conduct of the study. Dr Iber reported receiving grants from the University of Minnesota during the conduct of the study. Dr Wahlstrom reported receiving grants from the NIH during the conduct of the study. Dr Laska reported receiving grants from the NIH and the Centers for Disease Control and Prevention during the conduct of the study. Dr Redline reported receiving consulting fees for attending a scientific advisory meeting on Excessive Daytime Sleepiness funded by Jazz Pharmaceuticals plc. Dr Erickson reported receiving grants from the NIH during the conduct of the study. No other disclosures were reported.
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PubMed: MeSH publication types
- Journal Article
- Multicenter Study
- Observational Study
- Research Support, N.I.H., Extramural