Objective To determine whether simultaneous school start time changes (delay for some schools; advance for others) impact adolescents' sleep. Design Quasi-experimental study using cross-sectional surveys before and after changes to school start times in September 2015. Setting Eight middle (grades 7-8), 3 secondary (grades 7-12), and 8 high (grades 9-12) schools in Fairfax County (Virginia) public schools. Participants A total of 2017 (6% of ~34,900) students were surveyed before start time changes, and 1180 (3% of ~35,300) were surveyed after. Intervention A 50-minute delay (7:20 to 8:10 AM) in start time for high schools and secondary schools and a 30-minute advance (8:00 to 7:30 AM) for middle schools. Measurements Differences before and after start time changes in self-reported sleep duration and daytime sleepiness. Results Among respondents, 57.5% were non-Hispanic white, and 10.3% received free or reduced-priced school meals. Before start time changes, high/secondary and middle school students slept a mean (SD) of 7.4 (1.2) and 8.4 (1.0) hours on school nights, respectively, and had a prevalence of daytime sleepiness of 78.4% and 57.2%, respectively. Adjusted for potential confounders, students with a 50-minute delay slept 30.1 minutes longer (95% confidence interval [CI], 24.3-36.0) on school nights and had less daytime sleepiness (−4.8%; 95% CI, −8.5% to −1.1%), whereas students with a 30-minute advance slept 14.8 minutes less (95% CI, −21.6 to −8.0) and had more daytime sleepiness (8.0%; 95% CI, 2.5%-13.5%). Conclusions Both advances and delays in school start times are associated with changes in adolescents' school-night sleep duration and daytime sleepiness. Larger changes might occur with later start times.
Bibliographical noteFunding Information:
Support for this study was provided in part by grants ( 72549 , 73364 , and 73346 ) from the Robert Wood Johnson Foundation . The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official views of the Robert Wood Johnson Foundation. The funder had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
© 2017 National Sleep Foundation.
- Sleep duration
- Sleep timing