It’s not just how long teens sleep, but when, that’s important to self-regulation

teen sleep

Chronic insufficient sleep is at epidemic levels in U.S. teens. It’s been associated with depression, substance use, accidents and academic failure. But according to a survey of some 2,000 7th to 12th graders in Fairfax County, VA, the number of hours of sleep isn’t the core problem. It’s being a “night owl” — unable to fall asleep until late at night.

Forced to get up early for school, night owls are in a state of chronic “jet lag” on school days. And that can lead to poor self-regulation, or an inability to alter thinking, emotions and behaviors to meet varying social demands, finds the study, published last week by Pediatrics.

“Our results suggest it’s not how long you sleep that has the biggest impact on self-regulation, but when you sleep in relation to the body’s natural circadian rhythms and how impaired you are by sleepiness,” says Judith Owens, MD, MPH, director of the Sleep Center at Boston Children’s Hospital and first author on the paper.

Night owls, or teens with a so-called “evening chronotype,” and teens who reported daytime sleepiness reported significantly worse self-regulation, agreeing with such statements as “I forget instructions easily” and “It bothers me when I have to deal with changes.” Little wonder adolescents are moody!

To be sure, sleep duration, daytime sleepiness and circadian pattern were interconnected; night owls slept less on school nights and were sleepier in the daytime, as were those who slept fewer hours. And to be sure, 1 in 5 teens in the study were getting less than seven hours of sleep on school nights versus the recommended eight to 10.

But when the researchers examined all three aspects of sleep together and adjusted for age, sociodemographic factors and mental health conditions like ADHD, depression and anxiety, only daytime sleepiness and “night owl” tendencies independently predicted impaired self-regulation. Sleep duration did not.

A call for later school start times

Owens takes the survey findings as supporting her crusade for later start times for middle schools and high schools. In 2014, she was lead author on a policy statement from the American Academy of Pediatrics calling on middle and high schools to delay the start of class to 8:30 a.m. or later.

“The ‘misalignment’ or mismatch between early school start times and teens’ circadian rhythms — which normally shift later with puberty — may worsen self-regulation or so-called ‘executive functioning,’” she says.

Some schools start as early as 7 a.m., forcing many teens to wake up when they are at their lowest level of alertness — the equivalent of 3 a.m. for adults, write Owens and colleagues. That also means missing out on rapid-eye-movement (REM) sleep, which is concentrated in the early morning hours and is critical for forming memories and learning new information. Late bedtimes and late wake times on weekends only make the “social jet lag” worse come Monday.

“A recent report from the Centers for Disease Control and Prevention found that fewer than 20 percent of public middle and high schools in the U.S. start at the recommended time,” Owens says. “We hope the results of this study will add to the mounting scientific evidence supporting healthy school start times.”

Robert Whitaker, MD, MPH, at Temple University co-led the study. The research was supported in part by the Robert Wood Johnson Foundation (grants 72549, 73364, 73346). Check out the coverage by National Public Radio, The Atlantic, Health Day, and Fox News.