A growing body of evidence demonstrates that growing bodies benefit from more sleep. When districts push back the start of the school day, good things happen.
August 23, 2010|By Emily Sohn, Special to the Los Angeles Times
"These kids get into a vicious cycle of being exhausted, taking five hours to do three hours of homework and having to stay up later to get it done," she says. "As they're getting less sleep, they have to stay up later and they get even more tired."
The melatonin shift
Blame biology not laziness for making teens push the snooze button over and over again. As kids approach puberty, scientists now know, there is a two-hour shift in when their bodies release melatonin, the hormone that causes sleepiness. As a result, teens and preteens find it impossible to fall asleep until about 11 p.m., even if they try to go to bed earlier. Yet teenagers still need an average of 9.25 hours of slumber each night.
On top of the shift in natural sleeping and waking times, Owens says, there is also a delay in when a severe dip in alertness occurs during the early morning hours. In adults, this low point hits between 3 a.m. and 5 a.m.; in adolescents, it falls between about 5 a.m. and 7 a.m. That means that, while their alarm clocks are telling teens to get out of bed and demanding that their brains perform, their bodies are screaming at them to keep sleeping.
"There's no doubt that schools starting before 8 or 8:15 are too early if you just do the simple math," says Amy Wolfson, who studies adolescent sleep at the College of the Holy Cross in Worcester, Mass. "You're not going to speak to anyone in my field who is going to say they think starting at 7:15 makes any sense at all."
And it's not just high school students who suffer from alarm clocks that blare at what feel like ungodly hours, Wolfson says. The melatonin shift may happen as early as age 10 or 11.
In a 2007 study in the journal Behavioral Sleep Medicine, Wolfson and colleagues found that middle school students in urban New England whose schools started at 7:15 were getting much less sleep, exhibiting more behavior problems and were tardy four times as often as kids who started school at 8:37. The eighth-graders at the earlier-starting school also got worse grades than their peers who slept more. (In this study, and others like it, researchers make sure that comparison schools are similar in size, socioeconomics, race and other factors that could affect outcomes.)
On average, sixth-graders get 8.4 hours of sleep on school nights, according to the 2006 report on adolescent sleep habits by the National Sleep Foundation. High school seniors get just 6.9 hours.
In addition to the mood, behavior and learning issues, scientists are starting to uncover more subtle ways that such chronic sleep loss can hurt kids. Some studies, for example, show that sleep deprivation compromises the immune system. Others suggest that, with too little sleep, the body releases higher levels of hormones that induce hunger, possibly contributing to growing rates of obesity.
Tired teens may also be more vulnerable to falling asleep at the wheel. In two studies one out of Kentucky published in 2008 and one done in Virginia that was presented at a sleep meeting earlier this year scientists linked early high school start times with higher rates of car accidents. (In the Virginia study, there were 65.4 car crashes for every 1,000 teen drivers in the city with an early start time and 46.2 per 1,000 in a neighboring city with a later start time a difference of 40%.)
To stay awake, young people often turn to coffee, soda, energy drinks and other caffeinated beverages. In a public high school in Massachusetts, 95% of polled students reported drinking caffeine in the prior two weeks, mostly in the form of soda and most often in the afternoon and evening, Wolfson and a colleague reported in June in the journal Health Education and Behavior.
There are no published guidelines for how much caffeine is too much for adolescents, Wolfson says, but the substance stays in the body for up to five hours. Even if caffeinated kids manage to fall asleep, caffeine worsens the quality of their sleep. Finally, no one knows how caffeine might affect developing brains although plenty of experts are concerned about the link between sugar in soda and weight gain.
As the sleep research piles up, a growing number of schools are moving toward later start times. No one has kept track of how many schools have made the change. But experts say they are fielding a growing number of calls from districts around the country asking for advice about whether and how to switch to later start times. And this spring, Wolfson says, the Centers for Disease Control and Prevention hosted a meeting of interdisciplinary sleep researchers to talk about school start times and teen sleep deprivation as national health issues.