Abstract
Sirs: Epidemiological studies traditionally provide insights into disease pathogenesis. In multiple sclerosis (MS) geographical variation in prevalence, migration and family studies have all contributed to the view that MS is due to environmental exposure in genetically predisposed individuals. Particular insights are gained when welldefined populations are closely monitored over time, as has occurred in Canada, France, Denmark and certain parts of the UK. There are suggestions that the incidence and prevalence of multiple sclerosis (MS) are increasing, possibly due to an increased incidence among women [1]. In Canada, reported ratio of female:male MS was probably equal in the early 1900s, whereas recent evidence suggests ratios may be approaching 3.2:1. It has further been suggested that this increase may be explained in terms of environmental triggers in females. The UK has a high prevalence of MS, with parts of Scotland providing figures of 184/100,000 [2], whereas LETTER TO THE EDITORS
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