FRIDAY, Jan. 8 (HealthDay News) -- In news that probably won't surprise the parents or teachers of adolescents, a new study finds that most U.S. teens aren't getting enough sleep each night.
In fact, the study found that almost 69 percent of high school students get less than seven hours of sleep nightly. Only about 8 percent of teens get the optimal amount -- nine hours or more -- every night.
"We found that overall, about two-thirds of high school students are getting insufficient sleep on an average school night," said study author Danice Eaton, a research scientist at the U.S. Centers for Disease Control and Prevention in Atlanta. Eaton added that females, blacks and students in higher grades tended to get the least shut-eye.
The findings were published online Jan. 4 in the Journal of Adolescent Health.
A lack of sleep can have significant consequences in many areas of a teen's life. "You can take virtually any problem with teens, and a lack of sleep will make it worse," said Dr. Jonathan Pletcher, an adolescent medicine specialist at the Children's Hospital of Pittsburgh.
"Other research has shown that a lack of sleep can increase depression, negative physical health like headaches, poor school performance, school absenteeism and drowsy driving," Eaton noted.
When teens do get a full night of quality sleep, past research has shown that their grades may even improve, particularly their math scores.
But, Eaton's study suggests that there's a long way to go before most teens are getting the right amount of sleep. Data for the study came from the 2007 Youth Risk Behavior Survey, which asked teens how much sleep they get on an average school night.
The researchers found that 68.9 percent of teens reported getting insufficient sleep, which the researchers defined as seven or fewer hours a night. Another 23.5 percent reported getting eight hours a night, but just 7.6 percent got nine or more hours, which is considered the optimal amount for teenagers, according to the study.
Almost three-quarters of the females in the study reported getting insufficient sleep compared to two-thirds of the males.
The researchers found racial differences as well, with 69.2 percent of whites, 71.2 percent of blacks and 65.6 percent of Hispanics reporting insufficient sleep.
Teens also tended to sleep less as they got older, the study found. Just under 58 percent of ninth graders said they got insufficient sleep, but by 12th grade that percentage had risen to more than 78 percent.
Eaton said that while the study wasn't designed to find out what's keeping teens up at night, other research has suggested that teen employment, social activities, caffeine consumption, sleep disorders and early school start times all likely play a role in teens' lack of sufficient sleep.
Another previous study, this one from the June 2009 issue of Pediatrics, found that the more electronic devices an adolescent had in the bedroom, the less sleep a teen tended to get. This same study also found that one-third of teens feel asleep at least twice during the school day.
So, what can parents do to help their teens get enough shut-eye?
"First, recognize that sleep is very important. Kids today have a lot of competing demands for their time, but it's extremely important that teens get eight or more hours of sleep -- optimally nine hours or more," Eaton said.