To examine the impact of a 30-minute delay in school start time on adolescents' sleep, mood, and behavior.
Participants completed the online retrospective Sleep Habits Survey before and after a change in school start time.
An independent high school in Rhode Island.
Students (n = 201) in grades 9 through 12.
Institution of a delay in school start time from 8 to 8:30 AM.
Main Outcome Measures
Sleep patterns and behavior, daytime sleepiness, mood, data from the Health Center, and absences/tardies.
After the start time delay, mean school night sleep duration increased by 45 minutes, and average bedtime advanced by 18 minutes (95% confidence interval, 7-29 minutes [t423 = 3.36; P < .001]); the percentage of students getting less than 7 hours of sleep decreased by 79.4%, and those reporting at least 8 hours of sleep increased from 16.4% to 54.7%. Students reported significantly more satisfaction with sleep and experienced improved motivation. Daytime sleepiness, fatigue, and depressed mood were all reduced. Most health-related variables, including Health Center visits for fatigue-related complaints, and class attendance also improved.
A modest delay in school start time was associated with significant improvements in measures of adolescent alertness, mood, and health. The results of this study support the potential benefits of adjusting school schedules to adolescents' sleep needs, circadian rhythm, and developmental stage.