By TIMOTHY W. MARTIN Wall Street Journal 09/27/2011
More than two-thirds of U.S. high school students don’t get enough sleep on school nights, and they’re more likely than their well-rested peers to drink, smoke, and seriously consider suicide, according to a federal study released Monday.
Sleep researchers have long known teens don’t get enough sleep, advocating that school districts start classes later. But this study is the first to assess on a national scale whether sleep deprivation is associated with risky health behaviors, according to the Centers for Disease Control and Prevention, which did the study.
The study didn’t assess whether lack of sleep causes teens to engage in risky behavior, however. Many overachieving high-school students lack sleep because they’re busy, experts note.
The study analyzed 11 health-risk behaviors between those who sleep at least eight hours a night—the CDC-recommended amount—versus those who slept less. About 69% of more than 12,100 teens in a 2007 survey said they got eight hours or less of nightly rest on school nights.
More than half of weary-eyed teens reported alcohol use, compared to 37% of more well-rested adolescents. Nearly a quarter of sleep-deprived teens smoked, compared to 15% of those who got a good night’s rest. Sleep deprivation also increased the likelihood a high-school student had seriously contemplated suicide, to 17% compared with 9.8%.
Tired teens were also more likely to be less physically active, use marijuana, be sexually active and feel sad or hopeless, among other behaviors. There was no link between television watching and a lack of sleep.
A chronic lack of sleep impairs the ability to comprehend consequences and increases the likelihood a teen gives in to peer pressure, the study said. More than half of those surveyed got six or seven hours of sleep on school nights. Some 10% reported five hours, and 5.9% said they got four hours or fewer.
The report doesn’t suggest that lack of sleep prompts teens to engage in unhealthy behaviors.
“An incorrect interpretation of this research would be that only sleepy kids have sex,” said Bill Albert, chief program officer at the National Campaign to Prevent Teen and Unplanned Pregnancy. “The CDC is only making associations, not suggesting a causal link.”
One problem is that the biological clock changes in adolescence, making many teens want to go to bed and get up roughly two hours later than they did before reaching puberty—often meaning later than the 8 a.m. hour that many schools start, said Lela McKnight-Eily, a researcher for the CDC’s Division of Adult and Community Health and the study’s lead author.
“During adolescence, there is a shift in certain hormones that occur with puberty that cause the circadian rhythm to change,” Dr. McKnight-Eily said.
The report used data from the national Youth Risk Behavior Survey and an unedited version was published online last week by Preventive Medicine.