title: Determinants and impact of sleep duration in children and adolescents: data of the Kiel Obesity Prevention Study.
abstract: OBJECTIVE
  This study investigates determinants of sleep duration and its impact on nutritional status, resting energy expenditure (REE), cardiometabolic risk factors and hormones in children/adolescents.
  
  
  METHODS
  In 207 girls and 207 boys (13.0+/-3.4 (6.1-19.9) years) body mass index standard deviation score (BMI SDS), waist circumference (WC) z-score, body composition (air-displacement plethysmography), REE (ventilated hood system; n=312) and cardiometabolic risk factors/hormones (n=250) were assessed. Greater than 90th percentile of BMI/WC references was defined as overweight/overwaist. Sleep duration, media consumption (TV watching/computer use), physical activity, dietary habits, parental BMI, socio-economic status and early infancy were assessed by questionnaire. Short sleep was defined as <10 h per day for children <10 years and otherwise <9 h per day.
  
  
  RESULTS
  Total 15.9% participants were overweight, mean sleep duration was 8.9+/-1.3 h per day. Age explained most variance in sleep (girls: 57.0%; boys: 41.2%) besides a high nutrition quality score (girls: 0.9%) and a low media consumption (boys: 1.3%). Sleep was inversely associated with BMI SDS/WC z-score (girls: r=-0.17/-0.19, P<0.05; boys: r=-0.21/-0.20, P<0.01), which was strengthened after adjusting for confounders. Short vs long sleep was associated with 5.5-/2.3-fold higher risks for obesity/overwaist (girls). After adjusting for age, REE (adjusted for fat-free mass) was positively associated with sleep in boys (r=0.16, P<0.05). Independently of age and WC z-score, short sleep was associated with lower adiponectin levels in boys (11.7 vs 14.4 microg/ml, P<0.05); leptin levels were inversely related to sleep in girls (r=-0.23, P<0.05). Homoeostasis model assessment-insulin resistance (r=-0.20, P<0.05) and insulin levels (r=-0.20, P<0.05) were associated with sleep (girls), which depended on WC z-score.
  
  
  CONCLUSIONS
  Age mostly determined sleep. Short sleep was related to a higher BMI SDS/WC z-score (girls/boys), a lower REE (boys), higher leptin (girls) and lower adiponectin levels (boys).
authors.affiliation: Institut für Humanernährung und Lebensmittelkunde, Christian-Albrechts Universität Kiel, Kiel, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Hitze
authors.forename: A
authors.initials: A
authors.lastname: Bosy-Westphal
authors.forename: F
authors.initials: F
authors.lastname: Bielfeldt
authors.forename: U
authors.initials: U
authors.lastname: Settler
authors.forename: S
authors.initials: S
authors.lastname: Plachta-Danielzik
authors.forename: M
authors.initials: M
authors.lastname: Pfeuffer
authors.forename: J
authors.initials: J
authors.lastname: Schrezenmeir
authors.forename: H
authors.initials: H
authors.lastname: Mönig
authors.forename: M J
authors.initials: MJ
authors.lastname: Müller
mesh_terms: D052242:Adiponectin / Q000097:blood*; D000293:Adolescent; D000367:Age Factors; D015992:Body Mass Index; D001837:Body Weights and Measures; D002648:Child; D003201:Computers; D004032:Diet / Q000592:standards; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D015994:Incidence; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D020738:Leptin / Q000097:blood*; D008297:Male; D009752:Nutritional Status; D009765:Obesity / Q000097:blood / Q000453:epidemiology / Q000209:etiology*; D012307:Risk Factors; D012737:Sex Factors; D012890:Sleep / Q000502:physiology*; D013690:Television; D013997:Time Factors; D055105:Waist Circumference; D055815:Young Adult
chemical_list: D052242:Adiponectin; D007328:Insulin; D020738:Leptin