The epidemiology of multiple sclerosis in Queensland, Australia.
An epidemiological survey of multiple sclerosis (MS) in the State of Queensland was undertaken with its prevalence day being the national census day on June 30th, 1981, 20 years after a regional survey within the State. The relationship between increasing prevalence of MS and increasing south latitude within the State of Queensland which was suggested by the 1961 study was confirmed in the present study. The prevalence rate had increased significantly over the 20-year period between the studies but the State remained a medium frequency zone for MS (prevalence rate between 5 and 29 per 100,000 of population). Although a real increase in disease frequency could not be excluded as a contributing factor to the rise in prevalence, it was most likely due predominantly to an increase in life expectancy amongst the MS population and also in differential migration of a population at a greater risk of developing MS than the indigenous population. The proportions of Australian-born patients who had migrated to Queensland from the higher risk southern regions of Australia or travelled overseas to countries known to be high-risk for MS prior to disease onset, had fallen between the two surveys thus exerting, if anything, a negative influence on the change in prevalence. Analysis of MS prevalence rates amongst migrant populations in Queensland as compared to the more southerly city of Perth in Western Australia, suggested that the risk of acquisition of MS may extend over a wider age range than is generally accepted. Finally, there was an absence of MS cases amongst the Aboriginal population in Queensland but it can only cautiously be concluded from this study that the disease is rare in these peoples.