Hotspots and trends in multiple sclerosis prevalence in Australia utilising disease-modifying therapy prescription data.

BACKGROUND

Multiple sclerosis (MS) prevalence has increased from 21,000 (95.5 per 100,000) in 2010 to 33,000 (131.1) in 2021. The geographic variation of MS in Australia has been previously examined at a state level but not at sub-state level. The objectives were to measure the prevalence at regional level, identify MS hotspots and investigate latitudinal/longitudinal gradients from 2018-2022.

METHODS

Disease modifying therapy (DMT) prescription data from 1st Jan, 2018-15th November, 2022 were retrieved from the Pharmaceutical Benefits Scheme at the local government area (LGA) level. Prevalence was estimated by dividing the total number of prescriptions in each LGA by the respective DMT dosing schedule. Standardised MS ratios (SMSR) were calculated for each LGA. Geographic variation was investigated with Bayesian spatial regression models adjusting for demographics, comorbidities and socioeconomic status.

RESULTS

From 2018-2022, 888,991 DMT prescriptions were dispensed. In 2022, the LGA with the highest prevalence (per 100,000) were Mitcham(159), Light(158), Mount Barker(156) (South Australia), Hepburn(158), Glenelg(157), Mount Alexander(157) (Victoria), Ravensthorpe(158) (Western Australia) and Narromine (157)(NSW). An overall trend to increase was seen at the LGA level. Western-Victoria, Eastern South Australia and Western-Tasmania were identified as consistent hotspots confirmed in sensitivity analysis. We also observed an association with longitude-for regions with an equivalent latitude, moving from the east coast to the centre of Australia, we saw an increase in SMSR.

CONCLUSIONS

The calculation of LGA crude prevalence and LGA hot spots can inform regional health service delivery. Further investigation is needed to understand the potential environmental and patient factors that contribute to these hotspots and increasing MS prevalence in Australia.