Regional and Temporal Variation in the Incidence of Multiple Sclerosis in Finland 1979–1993

Abstract

Previous surveys in Finland from the 1960s have documented an uneven geographic distribution of multiple sclerosis (MS). In the present study, the incidence of MS was studied during 1979–1993 in the western Vaasa and Seinäjoki regions and in southern Uusimaa. The overall difference between the western 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 Seinäjoki was more than twofold greater than the 5.2 per 100,000 incidence found in neighboring Vaasa. An increasing incidence trend was observed for men in Seinäjoki, and a decrease for both sexes in Vaasa, while in Uusimaa the incidence remained stable for both sexes. The different incidence trends could not be readily explained by differences in case ascertainment but suggest the effect of environmental factors that have modulated the incidence of MS during the 15-year study period.

Linkage disequilibrium between the MBP tetranucleotide repeat and multiple sclerosis is restricted to a geographically defined subpopulation in Finland

“…Differences have been observed at the level of sex ratio, disease course, and presenting symptoms. A lower female-to-male ratio (1.6 vs 2.4) was found in the recent incidence study 33 in Seinäjoki as compared to Uusimaa, a region in the southern Finland, where Helsinki, the capital city, is located. Moreover, primarily progressive MS was more common in Seinäjoki (30% of patients) as compared to Uusimaa (20% of patients), and motor symptoms were more common and sensory symptoms less common in Seinäjoki than in Uusimaa.…”

“…33,34,37 The incidence of 11.6/10 5 for definite MS is among the highest ever reported. 33 Moreover, remarkable familial clustering of MS has been reported in this region.…”

“…33,34,37 The incidence of 11.6/10 5 for definite MS is among the highest ever reported. 33 Moreover, remarkable familial clustering of MS has been reported in this region. 38,39 We have recently found subtle differences in the clinical and demographic profile of MS in the Southern Ostrobothnian region, especially in the health-care district of Seinäjoki, as compared to other parts of Finland.…”

“…In the total set of families, the association of the STR-long 1.27 kb allele with MS did not reach statistical significance (w 2 ¼ 2.38, 1 df, two-sided test P ¼ 0.12, one-sided test P ¼ 0.06). Our previous data sets included a high proportion of patients from the Southern Ostrobothnia with exceptionally high incidence and prevalence of MS 33,34 and, hence, we made a separate, geographically defined data set, in which at least one of the patient's parents was born in this region (Bothnia families, Figure 3). Interestingly, the results of the analysis differed clearly between the 98 Bothnia families and the 251 other families.…”

A two-stage study on multiple sclerosis susceptibility and chromosome 2q33

“…High incidence and prevalence as well as familial clustering of MS has been demonstrated in this region. [29][30][31] Moreover, we have recently found that the association between MS susceptibility and MBP tetranucleotide repeat polymorphism is restricted to this geographical region that, together with its distinctive population history, suggests that the founder effect contributes to the high risk of MS in this region. 25,26 Thus, there is a justification for analysing Bothnia families separately.…”