To what extent does physical activity explain the associations between neighborhood environment and depressive symptoms in older adults living in an Asian metropolis?

Purpose: This study aimed to examine physical activity (PA) as a mediator of both neighborhood environment-depressive symptoms associations and the moderating effects of living arrangements on these associations. Methods: 909 Hong Kong Chinese older adults aged 65 + years and living in pre-selected communities stratified by walkability and socio-economic status participated in this cross-sectional observational study. Exposure variables were objectively-quantified neighborhood attributes. The outcome measure was presence of depressive symptoms. Scores on validated Chinese versions of international PA questionnaires were examined as mediators of environment-depressive symptoms associations and of the moderating effects of living arrangements (living alone vs. living with others) on these associations. Results: Neighborhood connectivity, prevalence of public transport, and pedestrian infrastructure were positively related to depressive symptoms; and frequency of walking for transport was identified as a suppressor of these positive associations. Living arrangements moderated the associations of a considerable number of measures of access to destinations of daily living with depressive symptoms, and most of these moderating effects were partially mediated by frequency of walking for transport. Conclusions: Ultra-dense, well-connected, pedestrian-friendly, destination-rich neighborhoods may contribute to lowering the risk of depressive symptoms in Hong Kong older adults by enabling them to frequently walk to local destinations of daily living and, thus, maintain their independence and bond with the community. These potential pathways of influence appear to be particularly important for older adults living alone. Future studies need to identify mechanisms other than PA that contribute to unexplained environment-depression relationships.