Defining catchment boundaries and their populations for Aotearoa New Zealand's rural hospitals.

Introduction There is considerable variation in the structure and resources of New Zealand (NZ) rural hospitals; however, these have not been recently quantified and their effects on healthcare outcomes are poorly understood. Importantly, there is no standardised description of each rural hospital's catchment boundary and the characteristics of the population living within this area. Aim To define and describe a catchment population for each of New Zealand's rural hospitals. Methods An exploratory approach to developing catchments was employed. Geographic Information Systems were used to develop drive-time-based geographic catchments, and administrative health data (National Minimum Data Set and Primary Health Organisation Data Set) informed service utilisation-based catchments. Catchments were defined at both the Statistical Area 2 (SA2) and domicile levels, and linked to census-based population data, the Geographic Classification for Health, and the area-level New Zealand Index of Socioeconomic Deprivation (NZDep2018). Results Our results highlight considerable heterogeneity in the size (max: 57 564, min: 5226) and characteristics of populations served by rural hospitals. Substantial differences in the age structure, ethnic composition, socio-economic profile, 'remoteness' and projected future populations, are noted. Discussion In providing a standardised description of each rural hospital's catchment boundary and its population characteristics, the considerable heterogeneity of the communities served by rural hospitals, both in size, rurality and socio-demographic characteristics, is highlighted. The findings provide a platform on which to build further research regarding NZ's rural hospitals and inform the delivery of high-quality, cost-effective and equitable health care for people living in rural NZ.