Later start times give teens more sleep, better school performance

A recent study in Seattle found that later start times in high schools resulted in increased sleep duration and better performance in students.

Previous studies have shown that delayed school start times would benefit the nearly half of American teenagers who reported sleep difficulties that effect their daily functions, and could decrease their risk for excess weight gain caused by inadequate sleep.

“Teens are chronically sleep deprived in the United States, and the vast majority of them do not get the recommended 9 hours of sleep per night,” Gideon Dunster, a doctoral student in the department of biology at the University of Washington, told Infectious Diseases in Children.

Researchers monitored sophomore students from two high schools in the Seattle Public School District in 2016 and again in 2017, before and after the start time was pushed from 7:50 a.m. to 8:45 a.m. During a 2-week recording phase, students wore wrist activity devices to record their sleep-wake cycles and kept a sleep diary to confirm the devices’ accuracy. Students also completed multiple questionnaires during the 2-week period.

The medium increase in sleep after the postponed start time was 34 minutes (P = .0007, effect size = 0.353). Social jet lag, or the differences in sleep time from school days to nonschool days, was also monitored in the study. After controlling for oversleep during nonschool days due to sleep debt accrued during school days, researchers found a significant decrease in social jet lag from 2016 (median = 1.6; n = 81) to 2017 (median = 1.25; n = 76). The decrease in social jet lag allowed students to better align their sleep on school days with the circadian timing of their sleep.

“By delaying high school start times here in Seattle by 55 minutes, students were able to sleep over 30 minutes more each night, be more alert during the day, and we saw a median increase of 4.5% in grades,” Dunster said. “We also saw a drop in the number of first period absentees and tardies, specifically in the more economically depressed school that we studied but not in the more affluent school that we studied. Thus, it is possible that by delaying school start times we can help reduce achievement gaps between schools of high and low economic backgrounds. Taken together, we believe that delaying high school start times is a single intervention that can have many benefits for teens.” – by Erin Michael

Disclosures: The authors report no relevant financial disclosures.