The study, published in Pediatrics, followed 785 children from an average age of 9 until 12. The children's height and weight were measured in third grade and again in sixth grade, and their mothers provided information on how many hours of sleep they got per night.
Overall, mothers reported that children slept an average of nine hours per night and boys slept less than girls.
Lack of Sleep Linked to Overweight
The results showed that boys and girls who slept less in the third grade were more likely to be overweight by the time they reached the sixth grade, regardless of their weight in third grade. Sleep duration measured in sixth grade was also associated with overweight among children in the sixth grade.
Researchers found the likelihood of being overweight by the sixth grade decreased by 40% for each additional hour of sleep the child received three years earlier and by 20% among current sixth graders.
That protective effect was linked to earlier bedtimes rather than later wake times in the morning.
Sleep duration may affect the amount of children's exercise or affect hormones that regulate appetite, say researcher Julie C. Lumeng, MD, of the Center for Human Growth and Development at the University of Michigan, and colleagues.
Sleep Tips for School-aged Children
Children aged 5 to 12 require 10 to 11 hours of sleep. The National Sleep Foundation offers these tips to parents: