The precise nature of the link between short sleep duration and obesity remains unclear, said Mary A. Carskadon, professor of psychiatry and human behavior at Brown University's Alpert Medical School in Providence, R.I., and director of chronobiology at Bradley Hospital in East Providence.
"Evidence has shown that there are changes in satiety and in levels of the hunger hormones leptin and ghrelin," Carskadon said. "But there's also evidence that kids who are not getting enough sleep get less physical activity, perhaps simply because they're too tired. It's just not cut-and-dried."
The study authors noted that "reduced sleep duration has become a hallmark of modern society, with people generally sleeping one to two hours less than a few decades ago."
Experts say that adolescents and pre-pubertal children generally do best with 9.5 to 10 hours of sleep a night, younger children a bit more.
The one-year study, led by Yun Kwok Wing of The Chinese University of Hong Kong, used questionnaires to track the sleep habits, lifestyle, height and weight of 5,159 local children aged 5 to 15 years.
The findings, published in the November issue of Pediatrics, could be helpful in preventing and managing childhood obesity, the authors noted.
For now, parents should take note of their children's wake-sleep cycles in light of other behavioral and environmental factors, the researchers advised.
For more on children's sleep problems, see the Nemours Foundation.
SOURCES: Kristen Knutson, Ph.D., assistant professor of medicine, University of Chicago; Mary A. Carskadon, Ph.D., professor, psychiatry and human behavior, Brown University's Alpert Medical School, Providence, R.I., and director, chronobiology, Bradley Hospital, East Providence, R.I.; November 200
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