Researchers in the U.S. asked 272,077 people — who were teenagers in the study period of 1991 to 2012 — about how often they got seven or more hours of sleep, and how often they got less sleep than they should.
"Adolescent self-reported sleep has decreased over the past 20 years," study author Julie Maslowsky of the University of Texas in Austin and her co-authors concluded in the study "The Great Sleep Recession."
"Seven hours per night is two hours less than the nine hours recommended by the National Sleep Foundation, indicating a particularly concerning trend toward inadequate sleep for a large portion of U.S.adolescents at an important juncture in development."
About 30 per cent of 15-year-olds said they got what they considered enough sleep in 1991, compared with 24 per cent in 2012.
The findings reflect what sleep expert Reut Gruber, an associate professor of the department of psychiatry at McGill University in Montreal, sees with Canadian teens. Gruber said it reinforces the "robustness" of the decrease in sleep time in teens.
Nodding off in class
In Monday's issue of the journal Pediatrics, the U.S. researchers say it's unknown why teens are getting inadequate sleep. Data are scarce, they say, but add that speculation points to factors such as:- Increased internet and social media use.
- Pressure from more competition to get into post-secondary education.
- Rising rates of obesity, which has been linked with sleep deprivation.
Anya Bystram, 17, of Toronto said she often gets as little as three hours of sleep a night. She finds herself catching up with friends on social media until the wee hours, and feels the consequences in her school work.
"I probably end up falling asleep in first period and then just totally blanking out the rest of the day, just not paying attention," Bystram said.
The demands of part-time jobs and extracurricular activities have also been suggested as factors keeping teens up at night.
Recognizing that changes in puberty make it less likely for teens to fall asleep, some school districts in the U.S. have shifted to later start times with nice results, Maslowsky said.