Daytime sleep duration and the development of childhood overweight: the KOALA Birth Cohort Study.

Reduced nighttime sleep is a risk factor for childhood overweight, but the association between daytime sleep and overweight is unknown. The aim of this study is to evaluate daytime sleep duration as an independent risk factor for childhood overweight. Data from the KOALA Birth Cohort Study on daytime and nighttime sleep at 2 years (N = 2322), and body mass index (BMI) around 2, 5, 6, 7, 8 and 9 years were used. Multivariable general estimating equation regression analyses were performed to examine the associations of sleep duration with BMI (linear) and overweight (logistic). No associations between daytime sleep and BMI or overweight were found, whereas longer nighttime sleep was associated with lower BMI and lower risk of overweight persisting up to age 9. Daytime sleep duration is probably less relevant for prevention of childhood overweight.