Three clinical courses are noted in patients with MS. Roughly two-thirds have a relapsing and remitting course, with relapses lasting weeks to months. The remaining one-third of patients have either a relapsing and progressive course or a chronically progressive clinical course, which is more common with advanced age. The incidence of MS is 4.5 to 8 per 100,000, and the prevalence is greater than 50 per 100,000. 9 In the United States, the peak age of onset for either sex is during the third decade of life. Females are two to three times more likely to contract MS, and they do so at a younger age than men. Males, however, are more likely to have a chronically progressive disease course from the onset of symptoms. MS is two times more likely in whites than in blacks, and it is rare in Asian populations. There is a geographic MS distribution, with temperate climates of economically developed countries experiencing a higher prevalence. Communities of northern Europe and the United States have prevalence rates of up to 173 per 100,000 in the white population. In the northern hemisphere there is a diminishing MS prevalence gradient that runs from north to south, while the opposite is true in the southern hemisphere. In general, 5 to 10 percent of MS patients will sustain a malignant course, and 20 to 35 percent will have a very benign disease course. Pregnancy reduces by 50 percent the MS relapse rate, but relapse risk increases up to sixfold during the postpartum period.
Was this article helpful?