School start time and sleep patterns among U.S. adolescents: Results from the National Comorbidity Survey – Adolescent Supplement

Research indicates that inadequate sleep among adolescents has important implications for physical and mental health and school functioning. Several U.S. regional studies have reported beneficial results following delayed school start times, but national data with comprehensive evaluation of sleep patterns and school-level information are scarce. Using information from over7,000 students attending 245 schools who participated in the National Comorbidity Survey Adolescent Supplement, a nationally representative study of U.S. adolescents ages 13-18, we investigated associations between school start time and sleep patterns. Data from direct interviews with youth on weeknight bedtime (n=7,206) and sleep duration (n=7,216), and school characteristics based on school authority report were analyzed. School start time was associated with weekday bedtime (p<.0001), after adjustment for age, sex, school type, urbanicity and school employment. Median weeknight sleep duration was 7.86 (IQR: 1.47) hours with only 26.4% meeting the recommended 8.5 hours of weeknight sleep. For start times of 8:00am and earlier, a 1-hour increase in start time was associated with 39.53 (95%CI=21.37-57.69) additional minutes of sleep for boys and 5.82 (95%CI=-12.26-23.89) additional minutes of sleep for girls. Those with 1-hour later start times were more likely to report >8.5 hours of weeknight sleep (Boys: OR=2.84, 95%CI=1.37-5.91; Girls: OR=1.80, 95%CI=.92-3.50). Our findings are consistent with prior reports of suboptimal sleep among U.S. adolescents and suggest that later start times, particularly for schools starting at or before 8:00am, may positively impact sleep duration. Ultimately, we hope this may help to reduce the health consequences of insufficient sleep among adolescents.