Relation between sleep duration and BMI varies by age and sex in youth age 8-19.

OBJECTIVES

The objectives of this study were to (i) compare the strength of associations between sleep duration and body mass index (BMI) in middle childhood, and early and late adolescence; (ii) determine whether sleep duration in middle childhood predicts BMI in early or late adolescence; and (iii) examine the consistency of these associations by sex.

METHODS

Subjects included 313 children/adolescents aged 8-19 participating in a longitudinal cohort study on sleep and health. Participants were assessed at three time points approximately 4 years apart: ages 8-11, 12-15 and 16-19. BMI z-score (BMIz) was calculated using age and sex normative data from the Centers for Disease Control. Sleep duration was reported by the parent (ages 8-15) or the adolescent (ages 16-19).

RESULTS

[corrected] Half of the participants were male and 79% were Caucasian. Sleep duration had a negative linear association with BMIz for boys but not girls, and the magnitude of this association decreased with age. Sleep duration at age 8-11 predicted BMIz in early and late adolescence for boys but not girls, and associations were largely attenuated after adjusting for BMIz at age 8-11. The strongest predictor of adolescent BMIz was BMIz at age 8-11 for both boys and girls.

CONCLUSION

We conclude that the association between sleep duration and BMIz varies by sex and age, with stronger associations in boys and in middle childhood compared with adolescence.