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 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).