Sleep duration and adiposity in children and adults: observational and mendelian randomization studies

Abstract

Objective: This study used two complementary designs, an observational and a Mendelian randomization (MR) study, to assess whether sleep duration causes adiposity in children and adults.

Methods: In Hong Kong's “Children of 1997” birth cohort, the adjusted cross-sectional associations of sleep duration with BMI z score and obesity and overweight were assessed at ~11 years of age. Generalized estimating equations were also used to examine longitudinal associations of sleep duration at ~11 years with annual BMI z score and obesity and overweight at about 11 to 16 years of age. Using MR, this study assessed the association of genetically predicted sleep duration, based on 54 single-nucleotide polymorphisms, applied to genetic studies of adiposity in children (n = 35,668), men (n = 152,893), and women (n = 171,977).

Results: Longer sleep was cross-sectionally associated with lower BMI z score at ~11 years of age (−0.13 per category, 95% CI: −0.22 to −0.04) and at about 11 to 16 years of age longitudinally in girls (−0.39, 95% CI: −0.66 to −0.13). Using MR, sleep duration was inversely associated with BMI in children (−0.29 SD per hour, 95% CI: −0.54 to −0.04), but was not clearly associated with BMI in adults, particularly for women.

Conclusions: A small beneficial effect of sleep on BMI in children cannot be ruled out.