Is the association between sociodemographic variables and physical activity levels in adolescents mediated by social support and self-efficacy?

Objective: Analyze whether the association between sociodemographic variables and physical activity levels is mediated by psychosocial factors. Methods: This is a cross-sectional epidemiological study of public and private high school students in Joao Pessoa, Paraiba state, Brazil. A total of 2540 adolescents (57.0% female) were analyzed (16.4 +/- 1.2 years). Physical activity was estimated using a questionnaire, self-efficacy, and parents' and friends' social support by scales, all previously validated. Results: The association between sex and the physical activity level of adolescents was partially mediated by the social support of parents (beta= 0.79; p < 0.001) and friends (beta = 2.96; p <0.001), and the association between age and physical activity level was partially mediated by parents' social support (beta =0.78; p< 0.001). The associations between sex and age and physical activity levels of adolescents were mediated by the social support of parents and friends. Conclusions: Differences in physical activity levels between adolescent females and males and between younger and older adolescents may be partially explained by differences in social support provided by parents and friends. Implementation strategies to increase the social support of parents and friends may help reduce the differences in physical activity levels between these subgroups of adolescents. (C) 2018 Published by Elsevier Editora Ltda. on behalf of Sociedade Brasileira de Pediatria.