NPR reports on a year-long, city-wide study that proved one of those obvious things that for some reason we never act on: Teenagers do a heck of a lot better if you just let them stay up late and sleep in:
Researchers at the University of Washington studied the high school students both before and after the start-time change. Their findings appear in a study published Wednesday in the journal Science Advances. They found students got 34 minutes more sleep on average with the later school start time. This boosted their total nightly sleep from 6 hours and 50 minutes to 7 hours and 24 minutes.
“This study shows a significant improvement in the sleep duration of students, all by delaying school start times so they’re more in line with the natural wake-up times of adolescents,” says senior author Horacio de la Iglesia, a University of Washington researcher and professor of biology.
The study also found an improvement in grades and a reduction in tardiness and absences.
Teens’ biological bedtime is more like midnight, he says, and if parents expect them to go to sleep at 10 p.m., it often doesn’t work. “They’ll just lay in bed and not fall asleep,” he says. Of course, this means teens need to sleep later in the morning. “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.,” says de la Iglesia.
In the study, researchers compared two separate groups of sophomores enrolled in biology classes at two Seattle high schools, Franklin High School and Roosevelt High School. The first group of 92 students, drawn from both schools, wore wrist monitors to track their sleep for two-week periods in the spring of 2016, when school still started at 7:50 a.m. The wrist monitors collected information about light and activity levels every 15 seconds so researchers could determine when students were awake and when they were asleep.
In 2017, after schools changed start times to nearly one hour later, researchers looked at a group of 88 students taking the same biology classes. They also wore wrist activity monitors and kept a sleep diary.
You might think that when school starts later, teens will just stay up later. But that’s not what researchers found. Bedtimes stayed relatively constant and kids caught some extra sleep in the mornings. “We’ve put them in between a rock and a hard place where their biology to go to bed later fights with societal expectations,” says lead researcher Gideon Dunster, a graduate student studying sleep at the University of Washington.
“Thirty-four minutes of extra sleep each night is a huge impact to see from a single intervention,” says de la Iglesia.
The study also shows a link between getting more sleep and better academic performance. Students who took the biology class after the later start time got final grades that were 4.5 percent higher than students who took the class when it started earlier. That could be the difference between an A and a B, says de la Iglesia.
The number of students who were tardy or absent also decreased significantly, putting Franklin High School — which is in a low-income neighborhood — on par with students from a higher-income neighborhood.