SCIENTIST HAVE MADE THE FOLLOWING OBSERVATIONS:
- In the United States, there are estimated to be 400,000 people with MS.
Although more people are being diagnosed with MS today than in the
past, the reasons for this are not clear.
- Most people are diagnosed between the ages of 20 and 50, although it
can occur in young children and significantly older adults.
- Worldwide, MS occurs with much greater frequency in higher latitudes
(above 40° latitude) away from the equator, than in lower latitudes, closer
to the equator. Even within one geographic area, however, where latitude
and climate are fairly consistent, prevalence rates may differ significantly.
These differences demonstrate that geographical factors are not the only
ones involved.
- MS is more common among Caucasians (particularly those of northern
European ancestry) than other ethnic groups, and is almost unheard of in
some populations, such as Inuit, Yakutes, Hutterites, Hungarian Romani,
Norwegian Lapps, Australian Aborigines, New Zealand Maoris. Thus,
ethnicity and geography seem to interact in some complex way to impact
prevalence figures in different parts of the world.
- Scientists have long been searching for an infectious agent that might
trigger MS. While many different viruses have been suggested, including
rabies, herpes simplex virus, measles, corona virus, canine distemper
virus, HTLV-1, Epstein-Barr virus, among others, none has yet been
confirmed. Although no trigger has yet been identified, most MS experts
believe that some infectious agent is involved in initiating the disease
process.
- Migration from one geographic area to another seems to alter a person's
risk of developing MS. Studies indicate that immigrants and their
descendents tend to take on the risk level—either higher or lower—of the
area to which they move. The change in risk, however, may not appear
immediately. Those who move before the age of 15 tend to take on the
new risk themselves. For those who move after the age of 15, the
change in risk level may not appear until the next generation.
- MS is approximately two to three times more common in women than in
men, suggesting that hormones may also play a significant role in
determining susceptibility to MS.
- Genetic factors are thought to play a significant role in determining who
develops MS. The average person in the United States has about one
chance in 750 of developing MS. But close (first-degree) relatives of
people with MS, such as children, siblings or non-identical twins, have a
higher chance—ranging from one in 100 to one in 40.
- Certain outbreaks or "clusters" of MS have been identified, but the cause
and significance of these outbreaks are not known.
- Clearly, many unanswered questions remain. While it may be tempting
to try and find short-cuts to the answers, or to tell ourselves that we know
more than we actually do about who gets MS and why, we need to
recognize the complexities involved and look to future epidemiological
studies to help unravel the facts.
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