title: Factors that influence weekday sleep duration in European children.
abstract: OBJECTIVE
  To compare nocturnal sleep duration in children from 8 European countries and identify its determinants.
  
  
  METHODS
  Cross-sectional.
  
  
  METHODS
  Primary schools and preschools participating in the IDEFICS study.
  
  
  METHODS
  8,542 children aged 2 to 9 years from 8 European countries with complete information on nocturnal sleep duration.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Nocturnal sleep duration was assessed by means of a computer based parental 24-h recall. Data on personal, social, environmental, and behavioral factors were collected by means of standardized parental questionnaire. Physical activity was surveyed with accelerometers.
  
  
  RESULTS
  Nocturnal sleep duration in the participating countries ranged from 9.5 h (SD 0.8) in Estonia to 11.2 h (SD 0.7) in Belgium and differed significantly between countries (P < 0.001) in univariate as well as in multivariate analyses, with children from northern countries sleeping the longest. Sleep duration decreased by about 6 min with each year of age over all countries. No effect of season, daylight duration, overweight, parental education level, or lifestyle factors could be seen.
  
  
  CONCLUSIONS
  Sleep duration differs significantly between countries. Our findings allow for the conclusion that regional affiliation, including culture and environmental characteristics, seems to overlay individual determinants of sleep duration.
authors.affiliation: Department of Epidemiological Methods and Etiologic Research, Bremen Institute for Prevention Research and Social Medicine (BIPS), Germany .
authors.forename: Sabrina
authors.initials: S
authors.lastname: Hense
authors.forename: Gianvincenzo
authors.initials: G
authors.lastname: Barba
authors.forename: Hermann
authors.initials: H
authors.lastname: Pohlabeln
authors.forename: Stefaan
authors.initials: S
authors.lastname: De Henauw
authors.forename: Staffan
authors.initials: S
authors.lastname: Marild
authors.forename: Dénes
authors.initials: D
authors.lastname: Molnar
authors.forename: Luis A
authors.initials: LA
authors.lastname: Moreno
authors.forename: Charalampos
authors.initials: C
authors.lastname: Hadjigeorgiou
authors.forename: Toomas
authors.initials: T
authors.lastname: Veidebaum
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Ahrens
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D015992:Body Mass Index; D016009:Chi-Square Distribution; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005060:Europe; D005260:Female; D006801:Humans; D008297:Male; D012890:Sleep; D011795:Surveys and Questionnaires; D013997:Time Factors