Physical Activity, Sleep, and Symptoms of Depression in Adults—Testing for Mediation

Purpose Physical activity, sleep problems and symptoms of depression contribute to overall wellbeing. The factors are reciprocally associated, but the nature of these associations remains unclear. The present study examined whether sleep problems mediated the association between physical activity and depressive symptoms. Methods The eligible population (n = 3596) consisted of adults from the ongoing, population-based Cardiovascular Risk in Young Finns Study started in 1980. Participants' leisure-time physical activity was assessed with physical activity index (2007) and sleep problems with Jenkins' Sleep Questionnaire (JSQ) in 2007 and 2011. Depressive symptoms were measured using modified Beck Depression Inventory (BDI-II) in 2007 and 2012, from which the items reflecting sleep problems were excluded. Mediation analyses, through which the associations between the variables were examined, were adjusted for sex and a set of health-related covariates assessed in 2007 and 2011. Results Physical activity was associated with decreased levels of sleep problems and depressive symptoms (P 0.05). Conclusion Physical activity's favorable contribution to depressive symptoms was mediated partly by sleep, but the mediation effect disappeared after adjusting for the previous depressive symptoms in adulthood. Corresponding Author: Kaisa Kaseva, Department of Psychology and Logopedics, P.O. Box 9, 00014 University of Helsinki, Finland. E-mail: kaisa.kaseva@helsinki.fi, tel: +35844307773 The present study was funded by Academy of Finland (grant no. 258578), Ministry of Education and Culture, Kone Foundation and Urheiluopistosäätiö. CONFLICTS OF INTEREST: The authors have no conflicts of interest to declare. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. The results of the study do not constitute endorsement by American College of Sports Medicine. Accepted for Publication: 7 January 2019 © 2019 American College of Sports Medicine

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