First direct evidence that later school day really does help teenagers

By | December 13, 2018
students in class

Teenagers benefit from a late start

Caiaimage/Sam Edwards/Getty

Pushing back high school start times not only improves the quality of students’ sleep, it also boosts attendance and academic performance, according to a study of US school attenders. The study is the first to show this objectively – using wrist-worn activity monitors to measure sleep duration – rather than by relying on self-reported information on sleeping habits.

Teenagers naturally prefer late nights and lie-ins due to body clock shifts that occur during puberty. However, this preference does not align with the early start times of most schools. “You’re basically chopping off the last chunk of sleep they need,” says Horacio de la Iglesia at the University of Washington.

To address this problem, schools in Seattle decided to delay their start time from 7:50 to 8:45am from mid-2016 onwards. De la Iglesia and his colleagues decided to measure the impact by studying students before and after the change. To make the comparison as objective as possible they compared students taking a tenth-grade biology class in 2016 with their younger peers taking the same class in 2017. There were 94 students in the 2016 group and 84 in the 2017 group.

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Sleep gains

According to activity monitors worn on their wrists, the students in 2016 and 2017 went to bed at around the same time. But because they were able to sleep in later, the 2017 students snoozed for an extra 34 minutes per day on average.

This extra sleep was correlated with greater daytime alertness and 5 per cent higher second-semester grades on average. This may be because sleep plays a key role in learning and laying down memories, says de la Iglesia.

At one of the schools, class attendance also improved. Students in 2017 were late on two fewer days and had two fewer absences per year on average than the students in 2016.

These improvements could potentially be enhanced by pushing school start times back even later, says Gideon Dunster at the University of Washington, who co-authored the study. The new start time in Seattle extended average sleep duration from 6 hours and 50 minutes to 7 hours and 24 minutes, but this is still not enough, he says. “While students are getting more sleep, they are still not sleeping the average of 9 hours per night that is recommended.”

Dunster hopes that future trials will determine the school start time that best aligns with students’ circadian rhythms and optimises their sleep quality and learning capacity.

Journal reference: Science Advances, DOI: 10.1126/sciadv.aau6200

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