Tuesday, November 13, 2007

Too Little Sleep May Pose Obesity Risk

Children who do not get enough sleep may increase their risk for obesity, a new study has found.

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Stuart Goldenberg

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Shorter Sleep Duration Is Associated With Increased Risk for Being Overweight at Ages 9 to 12 Years (Pediatrics)The researchers recorded sleep times and body mass index of 785 children in third grade and then again in sixth. Children slept an average of 9.45 hours a night in third grade and 8.78 in sixth.

After controlling for sex, race, maternal education, sleep problems like nightmares and other variables, the authors found that for every hour that sleep time declined over the three years, children were about 40 percent more likely to be overweight. The protective effect came mostly from earlier bedtimes rather than later wake times.

The authors concede that some unmeasured variables could have affected the results. For example, they write, parents may use food to pacify irritable sleep-deprived children, or sleep-deprived children may request and receive food more often.

The reason for the association is unclear, but parents are apparently not to blame. “We examined lax parenting,” said Dr. Julie C. Lumeng, the lead author of the study, which appeared in the Nov. 5 issue of Pediatrics, “and lax parenting is not the explanation.”

Instead Dr. Lumeng, an assistant professor of pediatrics at the University of Michigan, suggested three other possibilities.

“First, children who are grumpy may be more likely to ask for food,” she said. “Second, children who don’t get enough sleep are more likely to be tired the next day and less likely to exercise.” A third possibility is the hormone leptin, which is associated with fat metabolism and released in the body in relation to the sleep cycle.

“A disrupted sleep cycle,” she said, “may interfere with how the body stores calories.”


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