Who is at risk for multiple sclerosis (MS)?

Charles R. Smith, MD
Multiple sclerosis is typically diagnosed in people of Northern European extraction, explains neurologist Charles Smith, MD. Watch as he discusses why women are diagnosed with MS three times more often than men.
Multiple sclerosis (MS) is considered an autoimmune disorder, in the same family as lupus, rheumatoid arthritis, Crohn's disease, juvenile diabetes mellitus, and ulcerative colitis. With the exception of diabetes mellitus and ulcerative colitis, autoimmune diseases are much more common in women than men. In the past, women diagnosed with MS outnumbered men by 2.5 to 1. More recent surveys have shown a ratio of 4 to 1.

The reason MS is becoming more frequent in women is unclear, yet we do know that sex hormones (estrogen, progesterone, and testosterone) play a role in MS. The exception to this gender discrepancy in MS is primary progressive MS, which is more common in men.

MS has traditionally been thought of as a condition that affects Caucasians more than other races. While this still holds true, we are seeing many more African Americans, Hispanics and other races diagnosed. Researchers in South and Central America are finding increasing rates of MS in those regions.

While MS remains very uncommon in Africa, we see a significant number of African Americans with MS here in the US. It is estimated that African Americans develop MS at half the rate of Caucasian Americans -- one in 1,500 people, rather than one in 750. Studies have also shown that MS may follow a more aggressive course in African Americans.

Finally, while MS is typically diagnosed in young adults (ages 20 to 40), we are coming to a better understanding of the wide variation in age at the time of diagnosis. Teenagers and children represent a significant minority of the MS community (estimates of those diagnosed with MS before 18 range from 5 to 9 percent).
Most people experience their first symptoms of multiple sclerosis (MS) between the ages of 20 and 40 years, 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 the elderly, 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 as 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 years seems to be significant in terms of the risk of 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 years 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.

This answer is based on source information from the National Institute of Neurological Disorders and Stroke.

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