Determinants and impact of sleep duration in children and adolescents: data of the Kiel Obesity Prevention Study

Background/Objectives: 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. Subjects/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 mu g/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). European Journal of Clinical Nutrition (2009) 63, 739-746; doi:10.1038/ejcn.2008.41; published online 30 July 2008