Associations of neighbourhood attributes with depression in mid-age and older adults: the moderating role of traffic-related air pollution and neighbourhood socioeconomic status

We aimed to examine whether features of the natural, built and socioeconomic neighbourhood environments were related to depressive symptoms in Australian mid-age and older adults; and whether traffic-related air pollution (TRAP) (NO2) and area-level SES moderated the associations. A total of 4141 of participants (Mage = 61 years) were included in this cross-sectional study. Neighbourhood environmental characteristics included percentages of parkland, blue space and commercial land use, population density (persons/hectare), street intersection density (intersections/km2) within 1 km residential buffers. Annual mean concentrations of nitrogen dioxide (NO2) were included. In total-effect models, greater street intersection connectivity was associated with fewer depressive symptoms. Population density was positively associated with depressive symptoms in direct-effect models. Residents from disadvantaged areas with low levels of NO2 and with greater commercial land use coverage reported fewer depressive symptoms. In contrast, residents were more likely to report depressive symptoms with greater coverage of commercial land use in high SES neighbourhoods with low levels of NO2. Street connectivity and population density play a role in the maintenance of mental health in older adults. NO2 and area-level SES are moderators of commercial land use-depression associations, and this knowledge can better inform planning of commercial destinations and facilities in urban environments.