title: Sleep duration and overweight in European children: is the association modified by geographic region?
abstract: OBJECTIVE
  To investigate differences and a possible effect modification by geographical region in the association between sleep duration and overweight.
  
  
  METHODS
  Cross-sectional.
  
  
  METHODS
  Primary schools and preschools in 8 European countries.
  
  
  METHODS
  7867 children aged 2 to 9 years.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Nocturnal sleep duration was assessed as part of a parental 24-h recall. Height and weight were measured by standardized procedures across centers. Data on personal, social, environmental and behavioral factors were collected using a standardized parental questionnaire.
  
  
  RESULTS
  Sleep duration differed (P < 0.001) between European regions and normal vs. overweight children. A dose-dependent inverse association between sleep duration and overweight could be seen, with crude odds ratios ranging from 1.73 (99% CI 1.33; 2.25) for sleeping between 10 and 11 h to 3.81 (99% CI 2.85; 5.09) for sleeping less than 9 h (reference category > 11 h). This persisted after adjustment, but remained significant only for sleeping less than 9 h per night (north: OR = 1.70; 99% CI 1.13; 2.58 vs. south: OR = 2.84; 99% CI 1.57; 5.12) if stratified by region. No effect modification by region could be found, but adjustment for region accounted for changes in the effect estimate for sleeping less than 9 h (OR = 2.22; 99% CI 1.64; 3.02). The association was stronger in school children than in preschool children.
  
  
  CONCLUSIONS
  Geographic region and related aspects-even if they do not seem to modify the association between sleep and overweight-should in any case be taken in consideration as a confounding factor on this association.
authors: Department of Epidemiological Methods and Etiologic Research, Bremen Institute for Prevention Research and Social Medicine (BIPS), Germany.
authors: Sabrina
authors: S
authors: Hense
authors: Hermann
authors: H
authors: Pohlabeln
authors: Stefaan
authors: S
authors: De Henauw
authors: Gabriele
authors: G
authors: Eiben
authors: Dénes
authors: D
authors: Molnar
authors: Luis A
authors: LA
authors: Moreno
authors: Gianvincenzo
authors: G
authors: Barba
authors: Charalampos
authors: C
authors: Hadjigeorgiou
authors: Toomas
authors: T
authors: Veidebaum
authors: Wolfgang
authors: W
authors: Ahrens
mesh_terms: D002648:Child; D002675:Child, Preschool; D015986:Confounding Factors, Epidemiologic; D003430:Cross-Sectional Studies; D005060:Europe / Q000453:epidemiology; D005260:Female; D005843:Geography; D006801:Humans; D007223:Infant; D008297:Male; D016017:Odds Ratio; D050177:Overweight / Q000453:epidemiology*; D012890:Sleep / Q000502:physiology*; D012893:Sleep Wake Disorders / Q000453:epidemiology*