Longitudinal epidemiology of multiple sclerosis in Townsville, Queensland, Australia, 2012-2022.

Background: Townsville (population=195,564, latitude=19.3°S) is the largest city in the Northern Queensland region of Australia, an area previously defined as a low/medium-prevalence zone for multiple sclerosis (MS). However, the epidemiology of MS in this region since 1981 is unknown.

Aims: To assess the 2012 to 2022 epidemiology of MS in Townsville.

Methods: Demographic/clinical data extracted from medical records of MS cases identified by public and private clinicians. Prevalence, and incidence and mortality rates estimated for 2012 and 2022 and age-standardised to the 2022 Australian population. Differences in estimates assessed by Poisson regression.

Results: Females and relapsing-remitting MS comprised most cases. The 2012 prevalence was 45.0/100,000 (50.4/100,000 age-standardised, F/M sex ratio=2.0). Prevalence increased by 188% in 2022, with a crude prevalence of 86.9/100,000 (91.7/100,000 age-standardised, F/M sex ratio=2.7). 2012-22 MS onset incidence rate was 3.8/100,000 person-years (age-standardised 3.5/100,000, F/M sex ratio=2.7). Mean age increased from 49.4 to 57.3 years. Age-standardised mortality rate was 0.9/100,000 person-years, with standardised mortality ratio=1.0.

Discussion: These results show that Townsville is a high-frequency region for MS, with prevalence and incidence on par with that seen at higher latitudes in Australia. These results have implications for clinical practice in the region and for organisational resource allocation.