. According to surveys by the National Sleep Foundation, 90 percent of American parents think their child is getting enough sleep. The kids themselves say otherwise. In those same surveys, 60 percent of high schoolers report extreme daytime sleepiness. In another study, a quarter admit their grades have dropped because of it. Over 25 percent fall asleep in class at least once a week.
The raw numbers more than back them up. Half of all adolescents get less than seven hours of sleep on weeknights. By the time they are seniors in high school, according to studies by the University of Kentucky, they average only slightly more than 6.5 hours of sleep a night. Only 5 percent of high-school seniors average eight hours. Sure, we remember being tired when we went to school. But not like today’s kids.
It has been documented in a handful of major studies that children, from elementary school through high school, get about an hour less sleep each night than they did 30 years ago. While parents obsess over babies’ sleep, this concern falls off the priority list after preschool. Even kindergartners get 30 minutes less a night than they used to.
There are many causes for this lost hour of sleep. Overscheduling of activities, burdensome homework, lax bedtimes, televisions and cell phones in the bedroom all contribute. So does guilt; home from work after dark, parents want time with their children and are reluctant to play the hard-ass who orders them to bed. All these reasons converge on one simple twist of convenient ignorance: Until now, we could overlook the lost hour because we never really knew its true cost to children.
Using newly developed technological and statistical tools, sleep scientists have recently been able to isolate and measure the impact of this single lost hour. Because children’s brains are a work-in-progress until the age of 21, and because much of that work is done while a child is asleep, this lost hour appears to have an exponential impact on children that it simply doesn’t have on adults.
The surprise is how much sleep affects academic performance and emotional stability, as well as phenomena that we assumed to be entirely unrelated, such as the international obesity epidemic and the rise of Attention Deficit Hyperactivity Disorder. A few scientists theorize that sleep problems during formative years can cause permanent changes in a child’s brain structure: damage that one can’t sleep off like a hangover. It’s even possible that many of the hallmark characteristics of being a tweener and teen—moodiness, depression, and even binge eating—are actually symptoms of chronic sleep deprivation.