Neighbourhood environments and depressive symptoms in later life

Neighbourhood environmental features, including green and blue spaces, access to amenities, traffic, and ambient air pollution, may influence mental health in later life. Depression in older adults is associated with morbidity, cognitive decline, and reduced quality of life. While cross-sectional studies have linked environmental features to depressive symptoms, longitudinal evidence remains limited. This study examined longitudinal associations between built and natural neighbourhood characteristics, ambient air pollution, and depressive symptoms in older adults.

Participants were 1031 adults aged 70-90 years from the Sydney Memory and Ageing Study, followed for up to 12 years. Depressive symptoms were assessed using a modified 14-item Geriatric Depression Scale. Environmental attributes, including tree canopy, parkland, blue space, built environment indicators, and air pollution (particulate matter (PM)_2.5 and nitrogen dioxide (NO₂)), were measured within 1 km-radius buffers around geocoded residential addresses. Generalised additive mixed models estimated associations of person-level average exposures and within-person changes over time with depressive symptoms.

Higher average tree canopy cover and an increase in commercial land were associated with lower depression scores. Unexpectedly, higher average proportion of parkland, within-person increases in tree canopy cover and decreases in NO₂ exposure were associated with increased depressive symptoms. Sub-analysis comparing participants who moved with those who remained at their original residence indicated that these unexpected associations were observed only among participants who relocated and subsequently reported more depressive symptoms. Other environmental attributes showed no significant associations in adjusted models.

Long-term exposure to greater neighbourhood tree canopy is associated with fewer depressive symptoms. Enhancing tree cover may support mental wellbeing in older populations. Other environmental characteristics appeared less influential over long follow-up periods, and mixed findings highlight the complexity and context-dependence of environmental impacts on late-life depressive symptoms.