High incidence and prevalence of multiple sclerosis in south east Scotland: evidence of a genetic predisposition

OBJECTIVE To determine the incidence and prevalence of multiple sclerosis in the Lothian and Border Health Board Regions of south east Scotland. METHODS Incidence study: all patients were identified in whom a diagnosis of Poser category probable or definite multiple sclerosis was made by a neurologist between 1992 and 1995. Prevalence study: all patients known to have multiple sclerosis who were alive and resident in the study area on 15 March 1995 were recorded. RESULTS The crude annual incidence rates of probable or definite multiple sclerosis per 100 000 population were the highest ever reported: 12.2 (95% confidence interval (95% CI) 10.8–13.7) in the Lothian Region and 10.1 (95% CI 6.6–13.6) in the Border Region. A total of 1613 patients with multiple sclerosis were resident in the study area, giving standardised prevalence rates per 100 000 population of 203 (95% CI 192–214) in the Lothian Region and 219 (95% CI 191–251) in the Border Region. Prevalent cases were more likely than expected to have a Scottish surname (risk ratio 1.24, 95% CI 1.14–1.34). CONCLUSIONS Orkney and Shetland were previously thought to have by far the highest prevalence of multiple sclerosis in the world: about double that found in England and Wales. However, the prevalence in south east Scotland is equally high, suggesting that the Scottish population as a whole has a genetic susceptibility to the disease, and undermining the hypothesis that patterns of infection specific to small sparsely populated island communities are important in the causation of multiple sclerosis.