The primary aim of this study was to describe the geography of serious mental illness (SMI) – type 2 diabetes comorbidity(T2D) in the Illawarra-Shoalhaven region of NSW, Australia and to identify the significant clusters and their locations. The secondary objective was to determine the geographic concordance if any, between the comorbidity and the single diagnosis of SMI and T2D.
Spatial analytical techniques were applied to clinical data to explore the above aims. The geographic variation in comorbidity was determined by Moran’s I at the global level and the local clusters of significance were determined by Local Indicators of Spatial Association (LISA) and Spatial scan statistic. Choropleth hotspot maps were created to visually assess the geographic convergence of SMI, diabetes and their comorbidity. Additionally, we used bivariate LISA to identify coincident areas with higher rates of both SMI and T2D.
The study identified significant geographic variations in the distribution of SMI –T2D comorbidity in Illawarra Shoalhaven. The high-risk clusters were mainly located in the urban areas. Comparison of comorbidity hotspots with the hotspots of single diagnosis SMI and diabetes further revealed a geographic concordance of high-risk areas again in the urban areas outside the major metropolitan.
The identified comorbidity hotspots in our study may serve as a basis for future prioritisation and targeted interventions. Further investigation is required to determine the spatially varying association between comorbidity risk and the associated neighbourhood socio economic determinants.