Does mapping regional variation of transient ischaemic attacks in Victoria demonstrate disease trends?.

Abstract

Background and Objective: Understanding of the prevalence and regional risk of transient ischemic attack (TIA) is important to planning health service. To our knowledge there are no previous attempts to map regional variation in TIA rate across Victoria, Australia or in other countries. We aimed to compare and map the incidence and Standardised Morbidity Ratio (SMR) of TIA between Victorian Local Government Areas (LGAs). Method(s): Victorian hospital administrative data between 2001-2011 were used to define TIA cases and patients' LGA of residence. Population data by LGA and geocodes of the shapefiles (boundary of LGA) for each LGA were obtained from the Australian Bureau of Statistics for the purpose of mapping TIA cases by location. Spatial regression accounting for age and hypertension was conducted using SpatialEpi package in R (version 3.2.0). Result(s): 43,088 cases of TIA were identified across 2001-2011. SMR across LGAs ranged between 0 to 9.98. Our choropleth map demonstrates the highest SMRs in the rural North-Western LGAs of Victoria. The lowest SMRs were observed in Melbourne and the Yarra Valley region. Spatial regression shows similar effect of higher rate (coefficient 2.27-2.54) in the North-Western LGA over 10 years. Conclusion(s): SMR for TIA based on LGA population is higher in North-Western Victoria compared to other regions. The lowest observed SMR is concentrated in Metropolitan Melbourne and surrounds.