STUDY OBJECTIVES: To compare nocturnal sleep duration in children from 8 European countries and identify its determinants. DESIGN: Cross-sectional. SETTING: Primary schools and preschools participating in the IDEFICS study. PARTICIPANTS: 8,542 children aged 2 to 9 years from 8 European countries with complete information on nocturnal sleep duration. INTERVENTIONS: Not applicable. MEASUREMENTS: 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. CONCLUSION: 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.
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