Child obesity: the sleep link

Less sleep, more fat?

Less sleep can increase a child’s risk of being overweight or obese, according to a study by researchers at the Johns Hopkins Bloomberg School of Public Health. Their analysis of epidemiological studies found that with each additional hour of sleep, the risk of a child being overweight or obese dropped by 9%. The results are published in the February 2008 edition of Obesity, the journal of The Obesity Society.

“Our analysis of the data shows a clear association between sleep duration and the risk for overweight or obesity in children. The risk declined with more sleep,” says Youfa Wang, MD, PhD, senior author of the study and associate professor with the Bloomberg School’s Center for Human Nutrition. “Desirable sleep behavior may be an important low cost means for preventing childhood obesity and should be considered in future intervention studies. Our findings may also have important implications in societies where children don’t have adequate sleep due to the pressure for academic excellence.”

The study reviewed 17 published studies on sleep duration and childhood obesity and analyzed 11 of them in their meta-analysis. The recommended amount of daily sleep varied between studies analyzed and with children’s age. Some research suggests that under-5s should sleep for 11 hours or more per day, children aged 5-10 should sleep for 10 hours or more per day, and children over 10 should sleep at least nine hours per day. The Hopkins researchers used these suggestions for their analysis.

The results of the analysis showed that children with the shortest sleep duration had a 92% higher risk of being overweight or obese compared to children with longer sleep duration. For under-5s, shortest sleep duration meant less than nine hours of sleep per day; for 5-10 year olds it meant less than eight hours of sleep per day, and for children over 10 it meant less than seven hours of sleep per day. The association between increased sleep and reduced obesity risk was strongly associated with boys, but not in girls.

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