Factors that influence weekday sleep duration in European children.

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.