SATURDAY, Sept. 1, 2007 (HealthDay News) -- If your kids are falling asleep in their morning cereal, check their cell phones -- even a tiny bit of nighttime chatting might be robbing them of needed sleep.
A new study found that teens who reported using their cell phones after bedtime just once a month nearly doubled their odds of being very tired a year later. Those who gabbed away after lights out once a week were more than three times as likely to be tired.
The study only looked at students in Flanders, Belgium. But one U.S. pediatrician said the findings probably hold true for American kids, too.
"You have a population that's always tired to begin with," said Dr. Irwin Benuck, an attending physician at Children's Memorial Hospital in Chicago. Add nighttime cell-phone use to the mix, and the findings are "very predictable and not surprising," added Benuck, who's familiar with the study.
Study author Jan Van den Bulck, a researcher at Katholieke Universiteit Leuven in Belgium, surveyed 1,656 secondary school students; the average age in one group was 13.7 years and 16.9 years in the other.
Only 38 percent of the teens surveyed said they never used their cell phones after bedtime. Using the phone right after lights out increased the risk of being "very tired" a year later by 2.2 times; those who talked or text messaged between midnight and 3 a.m. raised their risk nearly fourfold.
Van den Bulck blamed cell phone use for tiredness in about one-third of all the children. "There is no safe dose and no safe time for using the mobile phone for text messaging or for calling after lights out," Van den Bulck wrote in the study.
In an interview, the author said parents may be in the dark about the nighttime activities of their kids. "It is a very typical phenomenon -- kids grow up with new technologies that adults discovered at a much later age, and, as a result, they use these technologies in ways adults can't even imagine," Van den Bulck said. "Concerned parents often think they know what their kids are up to, but often they don't."
Why would using a cell phone just once a month raise the risk of tiredness? "Possibly kids who say they don't use their phone underestimate the real frequency of the behaviors. Or maybe once you've started considering using the phone, you remain 'switched on,' " Van den Bulck said. "After all, don't forget that cell phone use requires at least two people. People who call may expect to be called as well -- even if you don't call much, you may still end up being awake, awaiting a potential call."
So what's a parent to do? Simple, Van den Bulck said: Restrict or forbid cell phone use after bedtime. "To teenagers, I would say: Be strong! You may feel that you need to stay connected with your friends all night, but you gain nothing by tiring yourself out, which is what you would be doing."
The study is published in the Sept. 1 issue of the journal Sleep.
Learn more about kids and sleep from the Nemours Foundation.