Physical activity mediates the relationship between program participation and improved mental health in older adults

Objectives: There is an implicit assumption that increased physical activity (PA) levels are responsible for the mental health benefits resulting from participation in PA programs. Other factors associated with participation may in fact be responsible. The purpose of this study was to examine whether changes in PA mediated the effects of two PA programs (Active Choices [AC] and Active Living Every Day [ALED]) on mental health outcomes. Study design: Secondary data analyses of quasi-experimental study. Methods: A sub-sample of older adults who participated in AC (n = 744) and ALED (n = 853) were included in the current analyses. MacKinnon's product of coefficients was used to test change in PA as a mediator of the relationship between program dose and change in mental health outcomes (depressive symptoms, stress, and number of days with poor mental health). Results: Change in PA explained 19% (AC) and 13% (ALED) of the absolute effects of program dose on depressive symptoms, 18% (AC) and 14% (ALED) of the effects on stress, and 37% (ALED) of the effects on days with poor mental health. Conclusions: Mounting evidence from both epidemiological studies and controlled trials suggests that PA can improve mental health. This study adds that increasing PA levels may improve mental health in older adults in 'real-world' settings. (C) 2015 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.