High prevalence and increasing incidence of multiple sclerosis in the Norwegian county of Buskerud

The objective was to investigate the incidence of multiple sclerosis (MS) as well as estimate the prevalence as of 1 January 2014 in the southeastern Norwegian county of Buskerud.

All patients with MS living in Buskerud county in Norway between 01 January 2003 and 01 January 2014 were identified. Point prevalence of MS was identified on 01 January 2014.

We found a prevalence of 213.8 (95% CI 196.4-231.1) per 100 000. The sex ratio was 2.2:1 with a female prevalence of 293.4 (95% CI 264.7-322.2) per 100 000 and a male prevalence of 134.7 (95% CI 115.3-154.2) per 100 000. About 82% of our MS population had a confirmed relapsing-remitting MS at disease onset, while 16.8% had primary progressive MS. The mean annual incidence between 2003 and 2013 was 11.8 (95% CI 10.6-13.1) per 100 000.

This study shows a high incidence of MS in Buskerud county in southeastern Norway, and the incidence may still be on the rise. We found a relatively high prevalence of MS in our population, although this does correspond with the recently published national data. Further studies investigating both changes in incidence and possible factors causing the increasing incidence are warranted.