Regional and temporal variation in the incidence of multiple sclerosis in Finland 1979-1993

Previous surveys in Finland from the 1960s have documented an uneven geogra phic distribution of multiple sclerosis (MS), In the present study, the inc idence of MS was studied during 1979-1993 in the western Vaasa and Seinajok i regions and in southern Uusimaa. The overall difference between the weste rn and southern regions persisted; 8.7 per 100,000 in the western, and 5.1 per 100,000 in the southern region, The incidence of 11.6 per 100,000 in Se inajoki was more than twofold greater than the 5.2 per 100,000 incidence fo und in neighboring Vaasa, An increasing incidence trend was observed for me n in Seinajoki, and a decrease for both sexes in Vaasa, while in Uusimaa th e incidence remained stable for both sexes. The different incidence trends could not be readily explained by differences in case ascertainment but sug gest the effect of environmental factors that have modulated the incidence of MS during the 15-year study period. Copyright (C) 2000 S. Karger AG, Bas el.