Abstract
BackgroundThere 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.MethodsWe 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.ResultsIn 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.ConclusionsIn 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.
Highlights
There is a dearth of studies on the effects of the neighbourhood environment on adults’ cognitive function
The present study examined how interrelated aspects of the built and natural neighbourhood environment, including air pollution as a sequela of urban densification, correlate with cognitive function in mid-age and older Australians, and the extent to which these relationships are explained by physical activity and sedentary behaviours that have been previously linked [3], or are potentially linked [21, 22], to cognitive health (Fig. 1)
We hypothesised that neighbourhood built environment indicators of densification would show potentially beneficial effects on cognitive function via transportation [3, 4, 23] and leisure-time activities [3, 5, 23], and detrimental effects via poorer access to parks [7, 10], higher levels of air pollutants [9, 11, 18] and their impacts on leisuretime activities [5, 24, 25] (Fig. 1). In testing these hypotheses and unlike previous research [9], this study modelled interrelationships between neighbourhood environmental attributes enabling a more robust estimation of, and a distinction between, the total and direct effect of aspects of the environment on cognitive function as well as on physical activity and sedentary behaviours
Summary
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. The physical and social characteristics of urban residential neighbourhoods have been identified as major determinants of morbidity and mortality [2]. They are especially important to ageing populations whose mobility is often limited, making them more reliant on their immediate environment for daily living. While the impacts of neighbourhood characteristics on middle-age and older adults’ active lifestyle have been relatively extensively researched, the same cannot be said for impacts on cognitive function and the mediating role of physical activity and sedentary behaviours in these associations [8, 9]
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