A geospatial analysis of Type 2 Diabetes Mellitus and the food environment in urban New Zealand

The aim of this research is to analyse the spatial epidemiology of Type 2 Diabetes Mellitus (T2DM) and investigate associations with the built environment in urban New Zealand. Data on T2DM was sourced from the New Zealand Virtual Diabetes Register (2016), and data on environmental variables sourced from the Ministry for Primary Industries and Territorial Authorities (2013-2016). Novel measures of the built environment using an enhanced two-step floating catchment area model were established using data on fast food outlets, takeaways, dairy/convenience stores, supermarkets and fruit/vegetable stores. Rates of T2DM per 1000 population and standardised morbidity ratios were computed and visualised for all urban areas. Getis Ord was used to assess spatial clustering, and Bayesian modelling was used to understand associations between T2DM and environmental variables. Results indicate that T2DM is influenced by demographic factors, spatially clustered and associated with accessibility to environmental exposures. Health-promoting resources, such as fruit/vegetable stores, were shown to have a consistently protective effect on T2DM while those considered detrimental to health showed varying, and largely insignificant, associations. This is the first study in New Zealand to spatially quantify the effects of multiple environmental exposures on population level T2DM for all urban areas using a geospatial approach. It 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.