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Sex differences in the association between sleep and body mass index in adolescents.

Knutson KL

Department of Medicine, University of Chicago, IL 60637, USA. kknutson@medicine.bsd.uchicago.edu

OBJECTIVE: To determine whether an association between short sleep duration and increased body mass index (BMI) exists in a sample of U.S. adolescents. STUDY DESIGN: Public-use dataset of the National Longitudinal Study of Adolescent Health. Final sample included 4486 adolescents (51% female). Main outcome was BMI transformed into z-scores for age and sex using reference values from the Centers for Disease Control/National Center for Health Statistics. Overweight was defined as > or =95th percentile. Linear and logistic regression models were calculated. Sleep duration was self-reported in hours. A quadratic term for sleep was added to test curvilinear association. Covariates included age, race, parental education, activity and inactivity scores. RESULTS: Among males, linear regression indicated that sleep duration significantly predicted BMI z-score (Beta = -0.08, 95% CI: -0.12, -0.03). Logistic regression indicated that sleep duration predicted risk of overweight among males (OR = 0.90, 95% CI: 0.82, 1.00). Sleep duration was not a significant predictor among females in either regression model. Quadratic term for sleep was not significant for either sex. CONCLUSIONS: Longer sleep duration was weakly associated with lower BMI and risk of overweight among male adolescents only. This sex-related difference may be due to differences in the physiology of puberty or in sleep characteristics.

Published 16 December 2005 in J Pediatr, 147(6): 830-4.
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