%0 Journal Article
%T Increased Female MS Incidence and Differences in Gender-Specific Risk in Medium- and High-Risk Regions in Finland from 1981每2010
%A Markus Holmberg
%A Annukka Murtonen
%A Irina Elovaara
%A Marja-Liisa Sumelahti
%J Multiple Sclerosis International
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/182516
%X Background. MS incidence has increased among females, suggesting the presence of environmental effect. Object. Regional differences and temporal changes in gender-specific MS incidence were studied in Finland. Methods. Cases from Jan 1, 1981 to Dec 31, 2010 in Pirkanmaa, Seinˋjoki and Vaasa districts were included. The standardized incidence rates (SIR), incidences per 105 person years with 95% confidence intervals (CI), and female-to-male ratios (F/M) were determined by district. Results. 1617 cases were included. Compared to Pirkanmaa, the MS risk was 1.9-fold (95% CI: 1.7每2.0) greater in Seinˋjoki and 1.2-fold (95% CI: 1.1每1.4) in Vaasa, and the risk was high for both genders. The incidence trend stabilized in Seinˋjoki and Vaasa, accompanied by an increase in the F/M ratio. A steady increase in Pirkanmaa was accompanied by a high F/M ratio. Conclusion. A high female preponderance accompanied a general increase in incidence since the 1990s, suggesting the influence of environmental factors. In high-risk districts, increased MS risk prevailed in both genders. High risk reflects both genetic and environmental effects. These effects may be shared with autoimmune diseases such as type 1 diabetes mellitus; the incidence of which follows MS in Finland. Population-based case-control studies are needed to identify these factor effects. 1. Introduction MS incidence has increased, particularly among females [1每4], indicating the influence of environmental factors. The integration of magnetic resonance imaging (MRI) in diagnostic criteria since the 1990s and progress in immunomodulatory drug treatments have contributed to these increasing rates [5, 6]. Epidemiologically, MS is characterized by an uneven geographical distribution [7]. Studies performed since 1964 confirm this observation in Finland [8每10], which is located in Northern Europe between the latitudes 60 and 70∼N. High-risk areas in the western districts, Seinˋjoki and Vaasa, are characterized by an irregular incidence pattern, and an increased male risk was observed in Seinˋjoki in 1979每1993 [10]. We aimed to analyze the gender-specific incidence in high- and medium-risk areas in 1981每2010 to make inferences on the etiological factors correlated with high-risk groups. The incidence in the former medium-risk area Pirkanmaa [8] is studied for the first time. Incidence is regarded as the most important indicator of disease frequency, and changes in incidence reflect environmental factors in genetically stable populations. 2. Materials and Methods The districts examined in this study are shown in Figure
%U http://www.hindawi.com/journals/msi/2013/182516/