From urban neighbourhood environments to cognitive health: a cross-sectional analysis of the role of physical activity and sedentary behaviours

Abstract

Background There is a dearth of studies on the effects of the neighbourhood environment on adults’ cognitive function. We examined how interrelated aspects of the built and natural neighbourhood environment, including air pollution, correlate with adults’ cognitive function, and the roles of physical activity and sedentary behaviours in these associations. Methods We used data from 4,141 adult urban dwellers who participated in the Australian Diabetes, Obesity and Lifestyle 3 study on socio-demographic characteristics, neighbourhood self-selection, physical activity and sedentary behaviours, and cognitive function. Neighbourhood environmental characteristics included population density, intersection density, non-commercial land use mix, and percentages of commercial land, parkland and blue space, all within 1 km residential buffers. We also calculated annual mean concentrations of NO2 and PM2.5. Generalised additive mixed models informed by directed acyclic graphs were used to estimate the total, direct and indirect effects of environmental attributes on cognitive functions and the joint-significance test was used to examine indirect effects via behaviours. Results In the total effects models, population density and percentage of parkland were positively associated with cognitive function. A positive association of PM2.5 with memory was also observed. All neighbourhood environmental attributes were directly and/or indirectly related to cognitive functions via other environmental attributes and/or physical activity but not sedentary behaviours. Engagement in transportation walking and gardening frequency partially mediated the positive effects of the neighbourhood environment on cognitive function, while frequency of transportation walking mediated the negative effects. Conclusions In the context of a low-density country like Australia, denser urban environments with access to parkland may benefit residents’ cognitive health by providing opportunities for participation in a diversity of activities. A more fine-grained characterisation of the neighbourhood environment may be necessary to tease out the negative and positive impacts of inter-related characteristics of urban neighbourhood environments on cognitive function.

Urban Neighbourhood Environments, Cardiometabolic Health and Cognitive Function: A National Cross-Sectional Study of Middle-Aged and Older Adults in Australia

“…This could have led to us observing the positive direct effects of air pollutants on cognitive function. In fact, positive associations of NO 2 and PM 2.5 with walking for transport were observed in an earlier analysis of AusDiab data [23] and negative associations of NO 2 with mean arterial pressure were found in this study, suggesting that destinations supporting engagement in utilitarian walking and other activities were not accurately captured by the land-use measures used in this study. These findings highlight the need for an accurate and comprehensive characterisation of urban neighbourhood environments, encompassing all key interrelated features, in studies of environmental determinants of cognitive function.…”

“…no. 39/11) [21][22][23]. Details about AusDiab data collection procedures are provided elsewhere [20][21][22].…”

“…Street-network buffers of a 1-km radius were created around geocoded participants' residential addresses to define neighbourhoods. A 1-km radius was used because it corresponds to a 10-20 min walk, which is a common definition of a neighbourhood [23]. Four built environment, two natural environment and two ambient air pollution measures were computed.…”

“…These were population density (persons/ha), street intersection density (intersections/km 2 ), percentage of commercial land use, non-commercial land use mix (range: 0-1), percentage of parkland, percentage of blue spaces (e.g., lakes, coastlines and rivers) and annual average concentrations of nitrogen dioxide (NO 2 , units: ppb) and fine particulate matter <2.5 µm in aerodynamic diameter (PM 2.5 , units: µg/m 3 ). Details on these measures are provided elsewhere [23][24][25] and in the Supplementary Materials (Section S1).…”

Associations between Traffic-Related Air Pollution and Cognitive Function in Australian Urban Settings: The Moderating Role of Diabetes Status

“…We have hypothesised that these positive associations may exist due to higher road density being associated with easier access to cognition-enhancing destinations [18,40,41]. For example, commercial destinations that offer opportunities for cognition-enhancing activities, such as food outlets, shopping and entertainment venues, can be major sources of air pollution generated by high population volumes and, hence, traffic.…”