MS can affect people of any age, any gender, and any ethnic background. However, some people do have a higher risk. 

MS is significantly more common in women than men, by a ratio of as much as 3 to 1. It appears more frequently in Caucasians than in Hispanics or African Americans, and is relatively rare among Asians and certain other ethnic groups. MS is most commonly diagnosed in individuals between the ages of 20 and 40, although it can develop in young children, teens and older adults.

The risk for MS among the general population is relatively low. Individuals with a parent or sibling who is diagnosed with MS have a slightly increased risk.

In countries further from the equator, an increase in MS cases is noted. In the United States, the northern states (above the 37th parallel) have twice as many cases of MS as the southern states.