Multiple Sclerosis

Multiple Sclerosis

Who Gets MS?

Most people experience their first symptoms of MS between the ages of 20 and 40, but a
diagnosis is often delayed. This is due to both the transitory nature of the disease and
the lack of a specific diagnostic test—specific symptoms and changes in the brain must
develop before the diagnosis is confirmed.

Although scientists have documented cases of MS in young children and elderly adults,
symptoms rarely begin before age 15 or after age 60. Whites are more than twice as likely
as other races to develop MS. In general, women are affected at almost twice the rate of
men; however, among patients who develop the symptoms of MS at a later age, the gender
ratio is more balanced.

MS is five times more prevalent in temperate climates—such as those found in the
northern United States, Canada, and Europe—than in tropical regions. Furthermore, the age
of 15 seems to be significant in terms of risk for developing the disease: some studies
indicate that a person moving from a high-risk (temperate) to a low-risk (tropical) area
before the age of 15 tends to adopt the risk (in this case, low) of the new area and vice
versa. Other studies suggest that people moving after age 15 maintain the risk of the area
where they grew up.

These findings indicate a strong role for an environmental factor in the cause of MS.
It is possible that, at the time of or immediately following puberty, patients acquire an
infection with a long latency period. Or, conversely, people in some areas may come in
contact with an unknown protective agent during the time before puberty. Other studies
suggest that the unknown geographic or climatic element may actually be simply a matter of
genetic predilection and reflect racial and ethnic susceptibility factors.

Periodically, scientists receive reports of MS “clusters.” The most famous of
these MS “epidemics” took place in the Faeroe Islands north of Scotland in the
years following the arrival of British troops during World War II. Despite intense study
of this and other clusters, no direct environmental factor has been identified. Nor has
any definitive evidence been found to link daily stress to MS attacks, although there is
evidence that the risk of worsening is greater after acute viral illnesses.

the National Institute of Neurological Disorders and Stroke

References and Sources: Medline, Pubmed, National Institutes of Health.

last update: November 2005

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