Sleep-Deprived Teens Paying Price

(CBS/AP) They drive while drowsy, oversleep, and doze off in class: Many of America's adolescents are going through life sleep-deprived.

Only 20 percent get the recommended nine hours of shuteye on school nights, and more than one in four report sleeping in class, according to a poll by the National Sleep Foundation released Tuesday.

What's more, the poll finds that parents are mostly in the dark about their adolescents' sleep habits. While most students know they're not getting the sleep they need, 90 percent of parents polled believe their adolescents are getting enough sleep on school nights.

A quick sampling of teens by CBS News Correspondent Thalia Assuras found the poll was on-target., with most saying they have trouble getting up in the morning.

Carl Woock, a 17-year-old high school senior from Bethesda, Md., let Assuras follow him through a typical weekday, with exhaustion surfacing several times.

"In the competition between the natural tendency to stay up late and early school start times, a teen's sleep is what loses out," said Jodi A. Mindell of St. Joseph's University in Philadelphia.

"Sleep serves not only a restorative function for adolescents' bodies and brains, but it is also a key time when they process what they've learned during the day," said Mindell, who is also associate director of the Sleep Center at The Children's Hospital of Philadelphia.

School-aged children and teens need at least 9 hours of sleep a day, according to the National Center on Sleep Disorders Research at the Ntional Institutes of Health.

But Owens said puberty changes the body's "circadian rhythm."

"An 8- or 9- or 10-year-old is able to fall asleep at 9:00 at night," she told Assuras, "but a 13, 14, 15 year old has their circadian rhythm shifted, so that they're not able to fall asleep until 10, 11, or 12:00 at night naturally."

The Sleep Foundation's poll found that sixth-graders were sleeping an average of 8.4 hours on school nights, while 12th- graders sleep just 6.9 hours, two hours less than recommended.

Without enough sleep, a person has trouble focusing and responding quickly, according to NIH. And the agency said there is growing evidence linking a chronic lack of sleep with an increased risk of obesity, diabetes, heart disease and infections.