Incidence of Multiple Sclerosis Since the 1950s

Investigators evaluated the incidence of multiple sclerosis (MS) in a mandatory Denmark registry begun in 1950 that had 19,536 cases available for study.

Cumulative incidence rates (CIRs) in women increased between the 1950s and the 2000s, by 114% in women and by 30% in men. Mean age of onset trended higher during this interval, from 34 to 37 years for men and 33 to 36 years for women. The female-to-male ratio rose from 1.3 in the 1950s to 2.0 in the 2000s. Also from the 1950s to the 2000s, MS incidence according to age of onset increased the most in women ages 50 to 64 (the oldest group). The increase among men was also most pronounced in this age group, but less so than in women. The changing sex ratio did not appear clearly associated wit…