Multiple sclerosis epidemiology in Finland: regional differences and high incidence

OBJECTIVES: Studies on the east-west gradient of multiple sclerosis (MS) are scarce. In Finland, epidemiological differences have been only partially elucidated, but the MS risk is high, and it has been claimed that the occurrence follows a longitudinal gradient. In this register-based study, we updated the MS epidemiology in southwest Finland (SwF) and compared it to the easternmost hospital district, North Karelia (NK), for which no previous data exist.MATERIAL AND METHODS: Patients with ICD-10 code G35 were identified from hospital district administrative data. Patient records were reviewed to include only cases with a definitive diagnosis. Incidence period covered 5 years (2012-2016) and the prevalence date was December 31, 2016. Results were standardized using the direct method.RESULTS: 1184 persons had MS in SwF and 253 persons in NK at the end of 2016. The prevalence was 280/100,000 (95% Cl 264-296) in SwF and 168/100,000 (95% Cl 148-190) in NK (age-standardized for the European standard population 2013). During the incidence period, 211 new MS diagnoses were made in SwF and 49 in NK. The annual age-standardized (ESP 2013) incidence was 12.1/100,000 person-years (95% Cl 10.5-13.8) in SwF and 8.6/100,000 person-years (95% Cl 6.4-11.2) in NK in the age group 10-69 years.CONCLUSIONS: There are regional differences in MS epidemiology in Finland, possibly related to demographic, social and genetic circumstances but the retrospective nature and limited sample size of this study might introduce some uncertainty to the calculations. SwF is a region with a globally very high risk for MS. This article is protected by copyright. All rights reserved.</p

Changes in multiple sclerosis epidemiology in Finland over five decades

Finland is a high-risk region for multiple sclerosis (MS) with several epidemiological studies on the subject published since 1964, but these have not been comprehensively scrutinized. The objective of this study was to review previous studies of Finnish MS epidemiology, introduce new data on MS prevalence in western parts of Finland and do further analyses on data from previous studies. We performed a systematic search on articles regarding MS epidemiology in Finland in PubMed database, and all relevant articles were included in this review. MS prevalences in the western hospital districts of Vaasa, South Ostrobothnia and Pirkanmaa were calculated in 1980-2007 by using previously unpublished data obtained from a retrospective search from hospital administrative registries. To enhance comparability of the epidemiological figures, we calculated age-standardized prevalence of MS from the new data from western hospital districts and previous data from North Ostrobothnia, Southwest Finland and North Karelia. Marked regional differences in MS epidemiology were confirmed with concentration of the disease in the western and south-western parts of the country. The highest regional age-standardized MS prevalence of 288/100 000 was reported in South Ostrobothnia in 2007. A clear and stable increase in MS prevalence was observed through the decades, but the only marked increase in incidence happened in 1990s. Methodological differences hampered direct comparisons of different studies, highlighting the importance of common principles of reporting and standardizing the epidemiological figures. More comprehensive studies on MS epidemiology are still warranted to yield important information concerning the aetiology of the disease