Prevalence of multiple sclerosis in Vasterbotten County in northern Sweden

Objective- To estimate the prevalence and clinical characteristics of multiple sclerosis (MS) in Vasterbotten County in northern Sweden. Methods -Individuals with MS were identified from several sources. A follow-up interview and/or examination was performed in 94% of cases still living in the area during 1997 -99. Onset adjusted prevalence and a definition of onset symptoms were applied. Results - A total of 313 cases were identified, resulting in an onset adjusted crude prevalence of MS for January 1990 of 125/10(5) (95%, confidence interval(CI): 112-140). Female predominance was evident (163/10(5) (95% CI: 142-187) vs 86/10(5) (95% CI: 71-104)). Diagnostic coding registers were the most important source for identification of cases. Conclusions - The crude prevalence of MS in Vasterbotten was higher than previous reports from other major areas in Scandinavia. The adjusted prevalence was significantly higher when compared with a previous study from Goteborg, south-western Sweden. The methodology used in this study gives a high degree of case ascertainment and increases the comparability of multiple sclerosis epidemiological studies.