Prevalence and incidence of multiple sclerosis in Oppland County: a cross-sectional population-based study in a landlocked county of Eastern Norway

Risberg G, Aarseth JH, Nyland H, Lauer K, Myhr K‐M, MidgardR. Prevalence and incidence of multiple sclerosis in Oppland County – a cross‐sectional population‐based study in a landlocked county of Eastern Norway.
Acta Neurol Scand: 2011: 124: 250–257.
© 2010 John Wiley & Sons A/S. Objectives – We report the prevalence and incidence rates of multiple sclerosis (MS) in Oppland County, Norway. Methods – Records from all patients diagnosed with MS at the two Oppland County hospitals, Gjøvik and Lillehammer during 1989–2001 were evaluated. In addition, all general practitioners in Oppland County reported their patients into the study. Results – The age‐adjusted prevalence rate of definite MS was 174.4/ 100 000 on the prevalence day 1 January 2002. When the probable cases were included, the prevalence rate rose to 185.6/100 000. The highest prevalence rates were detected in the northern mountain areas, thus corroborating the results from previous local surveys 30–50 years ago. The prevalence of MS was statistically significantly associated with climatic, socioeconomic and geographic variables in the county. The age‐adjusted incidence of definite and probable MS in Oppland County was 6.6/100 000 during 1989–1993 increasing to 7.6/100 000 during 1994–1998. Discussion – We found the highest prevalence rates of MS ever reported in Norway. Our findings indicate a possible influence of environmental factors.