Teens get more sleep when school starts later

Circadian rhythms of adolescents are fundamentally different than adults, children

A newly published research study concludes that that when their high school classes start later that teenagers use the extra time to sleep in.

Study result published Dec. 12 in the journal Science Advances noted that teens at two Seattle high schools got more sleep on school nights after start times were later – a median increase of 34 minutes of sleep each night. The study was also reported online at EurekAlert, a publication of the American Association for the Advancement of Science

Researchers from the University of Washington and the Salk Institute for Biological Studies said that boosted the total sleep time on school nights from a median of six hours, 50 minutes under the earlier start time to seven hours, 24 minutes under the later start time. Data was drawn from wrist activity monitors, rather than relying solely on self-reported sleep patterns, to demonstrate that a later school start times benefit adolescents by letting them sleep longer each night.

“This study shows a significant improvement in the sleep duration of students, all by delaying school start times so that they’re more in line with the natural wake-up times of adolescents,” said Horacio de la Iglesia, a UW biologist professor who was the senior and corresponding study author.

Lead author Gideon Dunster, a US doctoral student, said that research to date shows that circadian rhythms of adolescents are simply fundamentally different from those of adults and children.

The churning of circadian rhythms in humans helps the mind and body maintain an internal “clock” that tells people when it is time to eat, sleep, rest and work on a world spinning once on its axis about every 24 hours. Human genes and external cues from the environment, like sunlight, combine to create and maintain this study hu of activity, but with the onset of puberty the circadian cycle lengthens in adolescents and also decreases the rhythm’s sensitivity to light in the morning. These changes cause teens to fall asleep later at night and wake up later in the morning relative to most children and adults.

Scientists generally recommend that teens get eight to 10 hours of sleep each night. According to a U.S. Centers for Disease Control and Prevention study in 2017, only one-quarter of high school age teens reported sleeping the minimum recommended eight hours a night.