Sleep duration and activity levels in Estonian and Swedish children and adolescents
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We aimed to examine the associations of sleep duration with time spent on sedentary, moderate and vigorous activities in children and adolescents. The sample consisted of 2,241 (53.5% girls) Estonian and Swedish children (9–10 years) and adolescents (15–16 years), from the European Youth Heart Study, in 1998–1999. Sleep duration was calculated by the difference between self-reported bedtime and time for getting up on a normal weekday. Sedentary time/physical activity was measured by accelerometry (valid data on 1,462 participants). Adolescents had lower odds than children, and Swedish higher odds than Estonian, of meeting the sleep recommendations (>9 h) (OR = 0.22, 95% CI 0.17–0.27; and 1.32, 1.07–1.61, respectively). Participants sleeping longer than 10 h spent more time on physical activities (all intensities) and less time on sedentary activities than those sleeping shorter durations (all P < 0.001). The associations with physical activity became non-significant after additional adjustment for age or sexual maturation (Tanner stages), whereas the associations with sedentary time became borderline significant (P = 0.09/0.03, for age and Tanner, respectively). In conclusion, these results do not suggest a link between sleep durations and activity in a relatively large sample of children and adolescents from two European countries. Consequently, the common assumption that physical activity is a mediator in the relationship between short sleep durations and obesity is not supported by our findings.
KeywordsSleep Exercise Childhood Adolescence
We are grateful to the participants of the ECPBHS and their parents and the whole ECPHSC study team. We also thank the Swedish participants and families, as well as the EYHS field-work team. We also want to thank Charlotte Goodrose-Flores for the English revision. The study was supported by grants from the Stockholm County Council. This study was also supported by grants from the Estonian Ministry of Education and Science (No 0180027 and 0942706) and the Estonian Science Foundation (No 6932 and 6788). This study is also being supported by grants from the Spanish Ministry of Education (EX-2008-0641), Swedish Council for Working Life and Social Research (FAS), the Swedish Heart–Lung Foundation (20090635); and the Spanish Ministry of Science and Innovation (RYC-2010-05957).
Conflict of interest
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