Geographical distribution of A seropositive myasthenia gravis population

INTRODUCTION: To assess age- and sex-specific myasthenia gravis (MG) occurrence and incidence in the different geographical regions in Norway and thereby to identify factors that may contribute to the development of MG. METHODS: Multiple Poisson regression analysis was used to assess variation in incidence dependent on year, gender and onset age in five geographically defined health regions. RESULTS: The study population comprised 419 individuals with first time seropositive tests from 1995 to 2007. Annual MG incidence ranged from < 1 to 14 per million, with an average of 7.04 per million for all five health regions combined. CONCLUSIONS: This is the first nation-wide epidemiological study of seropositive MG that elucidates the geographical differences within a country. The incidence of seropositive MG did not vary significantly between the regions. Mid-Norway tended to have a higher incidence, and North tended to have a lower incidence.