America's teenagers are starting school too early, in spite of a flurry of studies showing they need more sleep and national recommendations that school days start later, government health experts said Thursday.
A survey of U.S. school districts shows fewer than one in five middle and high schools rang the first bell at 8:30 or later -- the time recommended by the American Academy of Pediatrics (AAP).
"Among an estimated 39,700 public middle, high, and combined schools in the United States, the average start time was 8:03 a.m. Overall, only 17.7 percent of these public schools started school at 8:30 a.m. or later," the Centers for Disease Control and Prevention wrote in the agency's weekly report.
It's not the real-time data - the survey covers the 2011-2012 school year, because it takes time to gather and analyze the information. The AAP made its recommendation just last fall.
But it shows how big the shift will have to be if schools are to meet the recommendations. It typically takes a year or more for a school district to change start times for schools.
Hawaii, Mississippi, and Wyoming had no schools that started at 8:30 AM or later, while 75 percent or more of schools in Alaska and North Dakota did, the survey found.
"Getting enough sleep is important for students' health, safety, and academic performance," said Anne Wheaton, a CDC epidemiologist who led the study. "Early school start times, however, are preventing many adolescents from getting the sleep they need."
Many people argue that all that is needed is for kids to get to bed earlier. But research shows that teenagers often can't help staying up late.
"In puberty, biological rhythms commonly shift so that adolescents become sleepy later at night and need to sleep later in the morning," Wheaton's team wrote.
"These biological changes are often combined with poor sleep hygiene (including irregular bedtimes and the presence of televisions, computers, or mobile phones in the bedroom)," they added.
"The combination of delayed bedtimes and early school start times results ininadequate sleep for a large portion of the adolescent population."
The consequences of this are clear.
"Adolescents who do not get enough sleep are more likely to be overweight; not engage in daily physical activity; suffer from depressive symptoms; engage in unhealthy risk behaviors such as drinking, smoking tobacco, and using illicit drugs; and perform poorly in school," they wrote.
Yet less than a third of U.S. high school students get 8 hours or more of sleep on school nights.
Montgomery County, Maryland is one of the school districts that just changed its school start times to meet the new recommendations.
The county, which borders Washington D.C., struggled with the issue. Then-school superintendent Joshua Starr suggested moving high school starts by 50 minutes to help kids get more sleep but found it would cost $21 million a year to do it, and not all parents supported the plan.
"These are really tough budget times for school districts around the nation," a spokeswoman for the district said.
The compromise, which begins later this month, will end up costing nothing on balance. High schools will start 20 minutes later, at 7:45 a.m., while middle schools will start at 8:15. Elementary schools will start 10 minutes later - a move made not for the benefit of small children, who usually wake earlier than older kids, but to accommodate school bus schedules.
"Although 20 minutes may not be ideal for extending sleep time for all high school students, it is a move in the right direction," said Patricia O'Neill, president of Montgomery County's board of education, said in a statement.
One of the biggest barriers to moving school start times is school bus schedules. Most districts use the same buses and drivers to get elementary and high school kids to school. The longer the window of time that buses are on the road, the more it costs to pay the drivers.
If elementary school children are sent to school earlier, either staff has to be paid more to stay later or parents must adjust to an earlier end to the school day.
In the meantime, the CDC recommends getting kids onto a disciplined sleep schedule, limiting the use of smartphones, computers and other technology at night, and says parents should set a good example themselves.
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A British study of 300 children found that the greatest reduction of diabetes risk came when kids were active during early adolescence, at around age 13. Experts say it underscores the importance of exercise, especially among young teens.