There are 2,500,000 people in the world with multiple sclerosis (MS) and approximately 400,000 people in the U.S. with multiple sclerosis. Two to three times as many women as men have MS. Multiple sclerosis is more common among Caucasians (particularly those of northern European ancestry such as Scots) than other races, and is almost unheard of in some populations, such as Eskimos.
The average risk of developing multiple sclerosis is approximately 1 in 1000. However, if a close relative has multiple sclerosis, the risk increases to 1 in 100 to 1 in 50.
Multiple sclerosis is not contagious. Multiple sclerosis is also not directly hereditary, although genetic susceptibility plays a part in its development. Most people with multiple sclerosis are diagnosed between the ages of 20 and 50. Multiple sclerosis is rarely diagnosed in people under the age of 12 and over the age of 55.
In certain populations, a genetic marker has been linked to MS. A particular genetic trait occurs more frequently in people with MS than in those who do not have the disease.
Worldwide, multiple sclerosis occurs with much greater frequency in higher latitudes (above 40 degrees latitude) away from the equator, than in lower latitudes, closer to the equator. Some studies show that MS is five times more likely in temperate zones such as North America and Europe than in the tropics.
In the U.S., multiple sclerosis occurs more frequently in states that are above the 37th parallel than in states below it. From east to west, the 37th parallel extends from Newport News, Virginia, to Santa Cruz, California and runs along the northern border of North Carolina to the northern border of Arizona and including most of California. The MS prevalence rate for the region below the 37th parallel is 57 to 78 cases per 100,000 people. The prevalence rate for those above the 37th parallel is almost double that of those below the 37th parallel: 110 to 140 cases per 100,000 people.
An individual who is born in an area with a higher risk of developing MS and moves to an area of lower risk, acquires the risk of the new home if the move occurs before the individual is 15 years old.
Various studies have contributed to the opinion that early exposure to an environmental agent might be a triggering factor in people who are predisposed by genetic factors to develop multiple sclerosis.
For additional information on the relationship between genetics and multiple sclerosis, please visit the National Multiple Sclerosis Society website at http://www.nmss.org/
Updated: July 2010
