title: From sleep duration to childhood obesity--what are the pathways?
abstract: 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, β = -0.36 vs. β = -0.26; Q95, β = -0.87 vs. β = -0.47). Adjustment for cortisol and CrP did not yield this attenuation.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Biometry and Data Management, BIPS - Institute for Epidemiology and Prevention Research, University of Bremen, Bremen, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Börnhorst
authors.forename: Sabrina
authors.initials: S
authors.lastname: Hense
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Ahrens
authors.forename: Antje
authors.initials: A
authors.lastname: Hebestreit
authors.forename: Lucia
authors.initials: L
authors.lastname: Reisch
authors.forename: Gianvincenzo
authors.initials: G
authors.lastname: Barba
authors.forename: Rüdiger
authors.initials: R
authors.lastname: von Kries
authors.forename: Otmar
authors.initials: O
authors.lastname: Bayer
mesh_terms: D050154:Adiposity; D015415:Biomarkers / Q000378:metabolism; D015992:Body Mass Index; D002097:C-Reactive Protein / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006306:Health Surveys; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism; D007328:Insulin / Q000378:metabolism; D016014:Linear Models; D008297:Male; D015999:Multivariate Analysis; D009765:Obesity / Q000209:etiology* / Q000378:metabolism / Q000503:physiopathology; D050177:Overweight / Q000209:etiology; D012890:Sleep / Q000502:physiology*; D011795:Surveys and Questionnaires; D013997:Time Factors
chemical_list: D015415:Biomarkers; D007328:Insulin; D002097:C-Reactive Protein; D006854:Hydrocortisone