Obese adolescents sleep shorter, although most studies have been cross-sectional. A longitudinal study in Philadelphia followed 1390 children from age 14 to 18 years.2013 One weakness was that heights and weights used to calculate body mass index (BMI) were self-reported. Mean BMI increased from 14 to 18, with the greatest increase at the 90th BMI percentile. Each additional hour of sleep was associated with a significant decrease in BMI at all percentile points from 10th to 90th, but the association was strongest at the upper end of the BMI distribution. Helping adolescents sleep longer may be a valuable tool in preventing obesity.
Reviewer: David Isaacs, firstname.lastname@example.org