Multiple sclerosis is an inflammatory demyelinating disease that most often appears in young adulthood, with the incidence peaking around age 30 (Wingerchuk, 2011). Findings published in the journal Neurology (Wallin, et al., 2019) on February 15, 2019 estimate the 2017 prevalence of adults with MS in the United States to be 362 cases per 100,000, or 913,925. In addition, the study supports previous evidence of a 3:1 female to male ratio.
MS is more common in areas inhabited by people of northern European ancestry. It is more common in Europe, the United States, Canada, New Zealand, and some parts of Australia; it is much less common in Asia and rare in tropical and sub-tropical regions (Ascherio & Munger, 2016). With some notable exceptions, the global distribution of MS increases with distance north or south of the equator, although there is some evidence that the north-south incidence gradient may have disappeared in the northern hemisphere (Koch-Henriksen & Sorensen, 2011).
MS is an immune-mediated disorder and is thought by most to be autoimmune, though the specific antigen(s) have not yet been identified. The cause of MS involves both genetic and environmental factors.
Reviewed by Kassandra Munger, ScD, September 2020