Children who sleep more tend to weigh less

Children who sleep more tend to weigh less than children who sleep less, and they are less likely than their counterparts to be overweight five years later. That's one of the major findings of a new study published in the January/February 2007 issue of the journal Child Development.

Conducted by researchers at Northwestern University, the study looked at 2,281 children from a nationally representative survey called the Child Development Supplement of the Panel Survey of Income Dynamics. The children were ages 3 to 12 at the start of the study and 8 to 17 when follow-up information was collected.

Children's sleep was measured by the total number of hours they slept, the times they went to bed, and the times they woke up.

Children who slept more had lower BMI (body mass index) measures and were less likely to be overweight five years later than their counterparts who slept less, even when their BMI and overweight status and such factors as parents' income and education and the children's race and ethnicity were taken into consideration. Specifically, the researchers found that sleeping an additional hour reduced young children's chance of being overweight from 36 percent to 30 percent, while it reduced older children's risk from 34 percent to 30 percent.

Although the National Sleep Foundation recommends that children ages 5 to 12 get 10 to 11 hours of sleep each night and adolescents get 8 to 9 hours, the study found that on weeknights, 7-year-olds slept on average less than 10 hours. By age 14, weekday sleep time fell to 8.5 hours.

"Our results suggest that many American children are not sleeping enough," said lead researcher Emily K. Snell of the School of Education and Social Policy and the Institute for Policy Research at Northwestern University. "In addition, our results suggest that encouraging parents to put younger children to bed earlier and allowing both younger and older children to sleep longer in the morning, as well as encouraging school districts to avoid very early school start times, might represent one important and relatively low-cost strategy to add to other efforts to help reduce childhood weight problems."