1325Longitudinal epidemiology of MS in the Greater Hobart region, 1961 to 2019
Abstract Background The Greater Hobart region (42.3°S) of Tasmania has the highest frequencies of MS in Australia, this consistent across studies conducted over the last half century. However, the degree of excess compared to mainland sites like Newcastle (32.5°S) has declined over time. Methods Cases were recruited from clinic-based samples and other multiple other data sources. Prevalence date was 1 June 2019. 2019 prevalence and 2009-19 incidence and mortality rates were estimated. Prevalence and incidence and mortality rates were age/sex-standardised to the 1961 and 1954 Hobart populations, respectively, to allow longitudinal comparisons. Female:male prevalence and incidence sex-ratios were also assessed. Differences between timepoints were assessed using Poisson regression. Results 472 MS cases (female:71.4%) resident on prevalence day were identified, a crude prevalence=212.3/100,000 (155.8 age/sex-standardised), 57% increase vs 2009 and 388.0% vs 1961. The 2009-19 incidence rate=7.56/100,000 person-years (7.03 age/sex-standardised), 91% increase vs 2001-9 and 218.1% vs 1951-61. The 2009-19 mortality rate was 2.25/100,000 person-years (1.12 age/sex-standardised), comparable to 2001-9 (1.00). The age/sex-standardised prevalence-sex-ratio was 2.61, comparable to 2009 (2.65), but the incidence-sex-ratio was 2.68, 31% increase vs 2001-9 (2.05). Conclusions Prevalence and incidence continue to be high in Hobart, although the differences compared to lower-latitude Newcastle have attenuated significantly. Changes in lifestyle may underlie the deterioration of the latitudinal gradient of MS in Australia. Further investigation is required to define the factors that drive these associations. Key messages MS prevalence and incidence are still highest in Australia in southern Tasmania but the latitudinal variation is declining.