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Who Gets Mulitple Sclerosis?


Updated May 16, 2014

Multiple Sclerosis Prevalence:

Risk factors and the question of who gets multiple sclerosis (MS) is a bit complicated. Because researchers do not fully understand the causes of MS, they also do understand why some people get MS and others do not. Overall, MS is considered a rare disease. The average person in the US has a 1 in 750 chance of getting MS. Less than one tenth of one percent of US citizens have MS.

Prevalence in the US:

The National Multiple Sclerosis Society estimates that 400,000 people in the US have been diagnosed with MS. A 2007 study in the journal Neurology put the number of people with MS in the US at 180,000. This difference is explained by the methods used to estimate the total number of cases. The MS Society’s estimate is viewed as more realistic. Approximately 200 people are diagnosed with MS in the US each week. Estimates of the number of people living with undiagnosed MS vary widely.

Prevalence in the World:

Because MS is a difficult illness to diagnose, worldwide MS statistics are hard to find. The best estimate is that around 2.5 million people in the world have MS.


Women are 2 to 3 times more likely than men to become diagnosed with MS. Researchers believe that the hormonal differences in men and women account for higher risk in women. Hormones have a clear interaction with MS and are known to be protective during pregnancy. This relationship is just beginning to be explored.


If no immediate members of your family have MS, then your chances of having MS are 1 in 750. If you have a parent or sibling with MS, your risk increases to 1 in 100. If you have an identical twin with MS, your risk is 1 in 4. It is interesting that identical twins do not always both have MS, even though they share 100% of genetic information. This fact is why researchers have concluded that MS is not simply a genetic disease.

Ethnicity and Geography:

MS occurs more often in people of northern European descent, but other ethnicities may also have MS. This could be explained by the fact that MS occurs more frequently in regions that are farther from the equator (above 40 degrees latitude). Rates of MS in these northern regions can be as much as 5 times higher. If a person migrates from a high-risk region to a low risk region before the age of 15, they take on the lower risk. Researchers think that puberty (hormones) and geography may somehow interact to increase MS risk.


Most MS is diagnosed between the ages of 20 and 50, thought both childhood and late onset MS are possible. This is usually the age at which the first symptoms appear and a person begins the process of getting diagnosed with MS.

Is MS increasing?:

The rates of MS in the US are increasing each year. This could be explained by better diagnostic tests (especially improved MRI scans) and an increased awareness of MS. It may be that many more cases of MS were undiagnosed before MRIs became widely used.

MS Clusters:

There are odd geographical clusters with higher MS rates. Researchers are studying these clusters to learn what factors in the environment may increase MS risk. So far, nothing has been discovered – but these cluster studies have promise to identify the geographical and environmental risk factors for MS.


Multiple Sclerosis: Hope Through Research ; National Institute of Neurological Disorders and Stroke

National MS Society

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