The built environment and health: a spatial analysis of type 2 diabetes and childhood weight status in urban New Zealand.
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
The built environment is an integral aspect of everyday life. It provides the context in which individual behaviours are set and can affect both individual and population health. It is shaped by distal systematic drivers which influence demographic and epidemiological changes such as the globalisation of economic processes, urbanisation, mechanisation, changing agricultural and trade policies, and dietary transitions. These systematic drivers, in turn, influence local environments which act as proximal determinants of population outcomes. Subsequently, the contextual impact of the local built environment is considered to be an influential aspect of spatial disparities in population health outcomes.
The focus of this thesis is on health outcomes of high weight status in children and population level Type 2 Diabetes Mellitus (T2DM). The prevalence of these health issues has increased alongside societal, demographic and cultural changes. While there are various biological, behavioural and environmental risk factors which influence the development of these health issues there is still much to be learned about both direct and indirect causes. The overall aim of this thesis is to analyse the built environment in urban New Zealand and investigate associations with the spatial epidemiology of two health outcomes, high weight status in children and population level T2DM. Despite substantial research and significant public attention directed toward these health issues within Aotearoa New Zealand, there are still critical gaps in the spatial understanding of such health outcomes. Current literature also highlights a lack of research which focuses on T2DM. This thesis addresses such research gaps using an ecological approach to analysis which utilises Geographic Information Systems (GIS) and spatial epidemiological methods. This is the first study in New Zealand to spatially quantify the effects of multiple environmental exposures on health outcomes of both high weight status in children and population level T2DM, for all urban areas, using a geospatial approach. It establishes novel measures of the built environment using data on fast food outlets, takeaways, dairy/convenience stores, supermarkets, fruit and vegetable stores, physical activity facilities, and greenspace to assess potential associations between contextual factors and health outcomes. In the context of this study, the former three of these categories are considered unhealthy exposures and detrimental to overall health. The latter four categories, in contrast, are considered to be healthy exposures and health-promoting. This thesis has, in turn, made original contributions to the current body of knowledge by: (1) including the use of both established and novel approaches to measuring various aspects of the built environment, and (2) analysing spatial data on health outcomes of high weight status in children and population level T2DM for all urban areas of New Zealand and assessing potential associations with the built environment. Such analysis also provides the opportunity to assess how the built environment may relate to not only outcomes of multiple chronic health conditions, but also different population groups.
When considering relationships between measures of the built environment and socioeconomic deprivation, results of this study indicate that accessibility to both and unhealthy and healthy exposures is generally higher in the most deprived areas compared to the least deprived areas. This study also found some notable results when looking at the spatial distribution of both high weight status in children and population level T2DM, finding that T2DM is more spatially clustered than high weight status in children. Both health outcomes were also shown to be heavily influenced by demographic factors and associated with accessibility to environmental exposures. Interestingly, results show that both of these health issues may be more heavily influenced by health-promoting resources than those considered detrimental to health. Health-promoting resources were shown to have a consistently positive effect on both health outcomes, while those considered detrimental to health showed varying, and largely insignificant, associations. Caution must be exercised, however, to ensure that a balanced approach is taken within prevention efforts which addresses environmental factors as well as economic accessibility, individual behaviours and societal norms.
The current study has implications for both policy and future research efforts as a deeper knowledge of local environments forms a basis on which to better understand spatial associations between the built environment and health as well as formulate policy directed toward environmental influences on chronic health conditions. It is vital to consider such contextual influences in order to better understand the spatial epidemiology of chronic health conditions in Aotearoa New Zealand. Accounting for these contextual influences within both research and policy can not only enhance understandings of such health concerns, but can also identify opportunities for prevention efforts. This thesis has, in turn, provided insight into such associations and a base from which to further address the complexities of such issues using a geospatial approach.