The Contribution of the Neighbourhood Environment to the Relationship Between Neighbourhood Disadvantage and Physical Function Among Middle-Aged to Older Adults

Background

With the continuing increases in life expectancies in developed countries, an important public health goal is to ensure successful ageing—morbidity compression, maintenance of physical functioning and active engagement in life. It is well established that the onset of physical function decline begins in mid-life, and functional capacity is critical to maintaining mobility, independence and quality of life. A growing body of literature has found that residents of more disadvantaged neighbourhoods have significantly poorer physical function, independent of individual-level factors. However, the mechanisms through which neighbourhood environments are associated with this relationship remain largely unknown.

The overarching aim of this thesis was to investigate the contributions of the neighbourhood environment to the relationship between neighbourhood disadvantage and physical function among middle-aged to older adults: this was accomplished in three studies. First, I examined the relationship between neighbourhood disadvantage and physical function in the Australian context (Study One). Second, I investigated if this relationship is explained by neighbourhood-level perceptions of safety from crime and walking for recreation (Study Two). Third, I examined the contribution of neighbourhood walkability and walking for transport to the relationship between neighbourhood disadvantage and physical function (Study Three).

Methods

This program of research utilized secondary data from the How Areas in Brisbane Influence HealTh and AcTivity (HABITAT) study. HABITAT is a multilevel longitudinal study underpinned by a social ecological framework. It was conducted in Brisbane among adults aged 45-70 years living in 200 neighbourhoods. HABITAT commenced in 2007 and had subsequent data collection waves in 2009, 2011, 2013 and 2016. For this thesis, the 2013 data were utilised as physical function was first collected in 2013 (n= 6,520). The measure of neighbourhood disadvantage was derived from the Australian Bureau of Statistics’ (ABS) Index of Relative Socioeconomic Disadvantage (IRSD) scores. Physical function was measured using the Physical Function Scale (0 – 100), a component of the Short Form-36 Health Survey, with higher scores indicating better function. In Study Two, participants self-reported their perceptions of safety from crime using items from the Neighbourhood Environment Walkability Scale (NEWS) questionnaire, which were subsequently aggregated to the neighbourhood-level. Walking for recreation (minutes per week) was self-reported by participants. In Study Three, neighbourhood walkability measures (street connectivity, dwelling density and land use mix) was objectively measured and provided by the Brisbane City Council (the local government authority responsible for the jurisdiction covered by the HABITAT study). Walking for transport (minutes per week) was self-reported by participants.

The data were analysed using multilevel regression models (linear, binomial or multinomial). In instances where multilevel categorical models are undertaken, Markov chain Monte Carlo (MCMC) simulation will be employed to estimate odds ratio and 95% credible intervals. All data were prepared in STATA SE 13 and analyses were conducted using MLwiN version 2.35.

Results

Findings from Study One found that residents of more disadvantaged neighbourhoods had significantly poorer physical function. These associations remained significant after adjustment for individual-level socioeconomic position (SEP). Moving forward from the descriptive findings, Study Two found that neighbourhood-level perceptions of safety from crime and walking for recreation partly explained (24% in men and 25% in women) neighbourhood differences in physical function. In Study Three, I found that neighbourhood walkability and walking for transport did not explain the relationship between neighbourhood disadvantage and physical function.

Conclusion

Given the growing proportion of the ageing population in Australia and the resultant increasing pressure on neighbourhood and city infrastructure in Australia, it is important to understand the contributions of the neighbourhood environment in the relationship between neighbourhood disadvantage and physical function. Despite the complexity in understanding neighbourhood socioeconomic differences in physical function, the findings of this thesis suggest that the neighbourhood in which we live is important to physical function. To reduce neighbourhood inequalities in physical function, attention needs to be given to improve the perceptions of safety from crime in more disadvantaged neighbourhoods to encourage more walking for recreation. Living in a walkable neighbourhood is important to support more walking for transport, but may not be sufficient to reduce neighbourhood inequalities in physical function. A multi-faceted intervention is needed to create a healthy, liveable and equitable community for successful ageing.