Change in multiple sclerosis prevalence over time in Australia 2010-2017 utilising disease-modifying therapy prescription data

Objective: Determine the prevalence of multiple sclerosis (MS) in Australia in 2017 using MS-specific disease-modifying therapy (DMT) prescription data and estimate the change in prevalence from 2010. Methods: DMT prescriptions were extracted from Australia's Pharmaceutical Benefits Scheme (PBS) data for January-December 2017. Percentages of people with MS using DMTs (DMT penetrance) were calculated using data from the Australian MS Longitudinal Study. Prevalence was estimated by dividing the total number of monthly prescriptions by 12 (except alemtuzumab), adjusted for DMT penetrance and Australian population estimates. Prevalences in Australian states/territories were age-standardised to the Australian population. Comparisons with 2010 prevalence data were performed using Poisson regression. Results: Overall DMT penetrance was 64%, and the number of people with MS in Australia in 2017 was 25,607 (95% confidence interval (CI): 24,874-26,478), a significant increase of 4324 people since 2010 (p < 0.001). The prevalence increased significantly from 95.6/100,000 (2010) to 103.7/100,000 (2017), with estimates highest in Tasmania in 2017 (138.7/100,000; 95% CI: 137.2-140.1) and lowest in Queensland (74.6/100,000; 95% CI: 73.5-75.6). From 2010 to 2017 using the median latitudes for each state/territory, the overall latitudinal variation in MS prevalence was an increase of 3.0% per degree-latitude. Conclusion: Consistent with global trends, Australia's MS prevalence has increased; this probably reflecting decreased mortality, increased longevity and increased incidence.