Significantly increasing multiple sclerosis prevalence in Australia from 2010 to 2021

Multiple sclerosis (MS) prevalence is increasing globally.

To determine whether increased prevalence is continuing within Australia using our validated prescription-based ascertainment method.

We used methods employed in our 2010 and 2017 prevalence estimates. Disease-modifying therapy (DMT) prescriptions were extracted from Australia's Pharmaceutical Benefits Scheme data for January-December 2021. DMT penetrance was calculated using data from the Australian MS Longitudinal Study. We divided the total number of monthly prescriptions by 12 or 2 (except alemtuzumab), adjusted for DMT penetrance and Australian population estimates. Prevalences in Australian states/territories were age-standardised. 2021 prevalence estimates were compared with 2010 and 2017 prevalence estimates using Poisson regression.

Number of people with MS in Australia in 2021 was 33,335; an increase of 7728 from 2017 (30.2%) and 12,092 from 2010 (56.6%) and increasing at a faster rate than population change (+10.1%, +14.1%). Age-standardised prevalence was 136.1/100,000 (increased from 103.7/100,000 in 2017). The previously demonstrated positive latitudinal gradient in 2010 and 2017 persisted in 2021, with Tasmania (southernmost state) having the highest prevalence (age-standardised: 203.5/100,000) while northernmost states had the lowest.

In line with global trends, MS prevalence is escalating in Australia, particularly in higher-latitude states. MS prevention is crucial to halt this disturbing trend.