Occurrence of multiple sclerosis in central Finland: a regional and temporal comparison during 30 years

Abstract

We estimated the prevalence and incidence of multiple sclerosis (MS) in central Finland up to 2000. Rates were compared with those in other areas in Finland. MS cases were identified in the hospital registry by ICD codes for demyelinating diseases from 1979 to 2000. Cases with definite MS were included. Incidence and prevalence were calculated with 95% CI and standardization was performed using direct method. In 1993 prevalence was 59/10(5) (n = 153). Incidence in 1979-93 was 3.8/10(5) person-years (n = 126). Rates are similar to average in areas with known rates of MS in Finland but substantially less than the over twofold MS risk in the neighbouring district Seinajoki. Extended follow-up to 2000 in central Finland showed increasing prevalence up to 105/10(5) (n = 277) and a significant increase in incidence 1994-98 up to 9.2/10(5) (n = 105). At the same time the diagnostic use of MRI increased up to 97%. Central Finland represents an average risk area of MS when compared with other areas of Finland but still a high risk in global comparison. The recent rapid increase in both prevalence and incidence is largely accounted for by increased use of MRI.