Epidemiology of multiple sclerosis in Australia: With NSW and SA survey results

Abstract

Objectives (i) To determine the prevalence of multiple sclerosis (MS) in New South Wales and South Australia; (ii) to compare these prevalences with those in other areas of Australia and to determine the relationship between prevalence and latitude; (iii) to examine the relative contribution of genetic and environmental factors in the aetiology of the disease in Australia; and (iv) to ascertain whether there had been a change in the frequency of the disease since 1961. Results The crude prevalence of MS in New South Wales on prevalence day (National Census Day, 30 June 1981) was 37.2/100000 and the age‐standardised prevalence 36.6/100000. The female:male ratio was 2.3:1. The crude prevalence in South Australia was 29.4/100 000 and the age‐standardised prevalence 28.8/100000. The female:male ratio was 2.4:1. No Aborigines or Torres Strait Islanders with MS were identified. There was a significant increase in the prevalence with increasing south latitude in Australia, MS being about seven times more frequent in Hobart than in tropical Queensland, but no genetic differences were found in the surveyed population in different parts of Australia. A significant increase in the prevalence of MS occurred in most areas of Australia between 1961 and 1981, but this may not reflect a true increase in incidence. Conclusion The increasing prevalence with increasing south latitude cannot readily be explained by genetic susceptibility, and suggests that environmental factors are important for expression of the disease.

Trends in the epidemiology of multiple sclerosis in Greater Hobart, Tasmania: 1951 to 2009

“…Both studies demonstrated a significant latitudinal gradient characterised by higher prevalence and incidence rates with increasing latitude: the MS prevalence and incidence in Hobart (42.8°S) were nearly double that of Newcastle (32.9°S) and Perth (31.6°S). Indeed, other work has demonstrated that the MS prevalence in Hobart is over six times that of northern Queensland 4. This latitudinal gradient has also been observed in New Zealand,7 Japan,8 France9 and the USA,10 and has been borne out in meta-analyses of prevalence11 and incidence 12.…”

Timing of birth and risk of multiple sclerosis: population based study

“…These are powerful, seem to act at a broad population level,1 – 3 and may hold the key to disease prevention. The “parent of origin” effect, recently reported in MS,5 may suggest that, at least in part, environmental factors are maternally mediated and influence development in the nervous or immune system, or both.…”

“…Environment seems to influence risk at a population level, but specific details remain unclear. The most striking clue to the role of environment has always been the gradient with latitude, which is most obvious in Australia, where the risk in temperate Tasmania is fivefold that in subtropical Queensland5 6 but where ethnic origins are relatively uniform. The gradient is also seen in several other countries, including New Zealand7 and the United States 8.…”

Effect of immigration on multiple sclerosis sex ratio in Canada: the Canadian Collaborative Study

“…In many regions around the world the incidence of multiple sclerosis (MS) appears to be rising 1 2 3 4 5 6 7 8 9 10 11 12 13. Although this had been widely ascribed to improved ascertainment, studies in Canada showed this was a real increase;14 year of birth (YOB) was a significant predictor of sex ratio over more than five decades (p<1.0 −28 ).…”