There’s been a push over the last few years to get school systems to delay the start time for high schoolers, but one question keeps coming up. If the schools start later, will the students get more sleep, or will they just stay up later? A look at one school system shows it’s the former and not the latter.
When Seattle Public Schools announced that it would reorganize school start times across the district for the fall of 2016, the massive undertaking took more than a year to deploy. Elementary schools started earlier, while most middle and all of the district’s 18 high schools shifted their opening bell almost an hour later — from 7:50 a.m. to 8:45 a.m. Parents had mixed reactions. Extracurricular activity schedules changed. School buses were redeployed.
And as hoped, teenagers used the extra time to sleep in.
In a paper published recently, researchers at the University of Washington and the Salk Institute for Biological Studies announced that teens at two Seattle high schools got more sleep on school nights after start times were pushed later — a median increase of 34 minutes of sleep each night. This boosted the total amount of sleep on school nights for students from a median of six hours and 50 minutes, under the earlier start time, to seven hours and 24 minutes under the later start time.
“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 senior and corresponding author Horacio de la Iglesia, a UW professor of biology.
The study collected light and activity data from subjects using wrist activity monitors — rather than relying solely on self-reported sleep patterns from subjects, as is often done in sleep studies — to show that a later school start time benefits adolescents by letting them sleep longer each night. The study also revealed that, after the change in school start time, students did not stay up significantly later. Instead, they slept longer, a behavior that scientists say is consistent with the natural biological rhythms of adolescents.
“Research to date has shown that the circadian rhythms of adolescents are simply fundamentally different from those of adults and children,” said lead author Gideon Dunster.
In humans, the onset of puberty lengthens the circadian cycle in adolescents and also decreases the rhythm’s sensitivity to light in the morning. These changes cause teens to fall asleep later each night and wake up later each morning compared to younger children and adults.
“To ask a teen to be up and alert at 7:30 a.m. is like asking an adult to be active and alert at 5:30 a.m.,” said de la Iglesia.
Scientists generally recommend that teenagers get eight to 10 hours of sleep each night. But early-morning obligations, such as school start times, force adolescents to either shift their entire sleep schedule earlier on school nights or truncate it. Certain light-emitting devices — such as smartphones, computers and even lamps with blue-light LED bulbs — can alsointerfere with circadian rhythms in teens and adults alike, delaying the onset of sleep. According to a survey of youth released in 2017 by the U.S. Centers for Disease Control and Prevention, only one-quarter of high school age adolescents reported sleeping the minimum recommended eight hours each night.
The researchers hope that their study will help inform ongoing discussions in education circles about school start times. The American Academy of Pediatrics recommended in 2014 that middle and high schools begin instruction no earlier than 8:30 a.m., though most U.S. high schools start the day before then. In 2018, California lawmakers nearly enacted a measure that would ban most high schools from starting class before 8:30 a.m. In 2019, Virginia Beach, home to one of the largest school districts in Virginia, will consider changes to its school start times.
“School start time has serious implications for how students learn and perform in their education,” said de la Iglesia. “Adolescents are on one schedule. The question is: What schedule will their schools be on?”