Prevalence of multiple sclerosis in Flanders, Belgium.

Two hundred twenty patients fulfilling the Poser diagnostic criteria for definite and probable multiple sclerosis (MS) were ascertained in an area of Flanders (Belgium) including the city of Leuven through the general practitioners and the neurologists practicing in the area, through the medical records of the National Center for MS and through the membership list of the MS patient society. Leuven is located at a latitude of 50 degrees 53 N. A prevalence rate of 73.8 per 100,000 [95% confidence limits (95% CI) 58.7-89.0] for men and 101.3 (95% CI 80.4-114.5) for women, and of 87.9 for both sexes (95% CI 76.2-99.4) was found on October 1, 1991. This prevalence rate is not significantly different from rates recently reported for other areas in Europe at the same latitude. The female to male ratio however was only 1.41, which is significantly lower than that in neighboring regions.