Who Gets MS?
Approximately 400,000 individuals have been diagnosed with MS in
the United States and as many as two and a half million
worldwide, with an estimated 10,000 new cases diagnosed in the
United States annually. Most people with MS experience their
first symptoms and are diagnosed between the ages of 15 and 50.
The distribution of this disease is not
totally random. On average, women are three times as likely than
men to develop MS. Additionally, the occurrence of this disorder
is positively correlated with latitude. People living beyond the
40-degree mark north or south of the equator are far more likely
to develop MS than those living in the warmer climates near the
equator. This is especially true for people in North America,
Europe, and southern Australia, while Asia continues to have a
low incidence of MS. More prevalent among those of northern
European or Scandinavian ancestry, Caucasians are far more
likely than those of African heritage to develop this disease.
While MS is not contagious or
hereditary, MS susceptibility is increased if a family member
has MS. The average risk of developing MS in the United States
is one in 1,000, or one tenth of one percent. For first-degree
relatives (such as a child or sibling), the risk increases to
three or four percent. This is not true for adopted children or
half siblings (who do not share the same parent who has MS),
whose risk is the same as unrelated individuals. In instances
where one identical twin has been diagnosed with MS, the other
twin has a 31 percent risk of developing the disease. The risk
for twins who are not identical is five percent - similar to
that of other siblings.
Another factor linked to MS is
cigarette smoking. Women who smoke are 1.6 times more likely to
develop MS than women who are non-smokers. Additionally,
individuals with MS who smoke appear to be at a much greater
risk of experiencing a quicker progression of their disease.