From sleep duration to childhood obesity--what are the pathways?

Sleep duration has been identified as risk factor for obesity already in
children. Besides investigating the role of fat mass (FM), this study addressed
the question whether endocrine mechanisms act as intermediates in the association
between sleep duration and overweight/obesity. Within the framework of the
IDEFICS study, the present research was conducted in 609 German resident children
aged 2-9 years with information on fasting insulin, C-reactive protein and
cortisol levels next to anthropometric measurements and parental questionnaires.
Emphasising methodological aspects, an age-specific measure of sleep duration was
derived to account for alteration in sleep duration during childhood/period of
growth. Multivariate linear regression and quantile regression models confirmed
an inverse relationship between sleep duration and measures of
overweight/obesity. The estimate for the association of sleep duration and body
mass index (BMI) was approximately halved after adjustment for FM, but remained
significant. The strength of this association was also markedly attenuated when
adjusting for insulin mainly for the upper BMI quantiles (Q80, ? = -0.36 vs. ?
= -0.26; Q95, ? = -0.87 vs. ? = -0.47). Adjustment for cortisol and CrP did not
yield this attenuation. Conclusion: The inverse relationship between sleep
duration and BMI is mainly explained by the association between sleep duration
and FM. Insulin may explain part of this association, in particular at the upper
tail of the BMI distribution.