Who Gets Multiple Sclerosis
Approximately 400,000 individuals have been diagnosed with MS in the United States and as many as 2.5 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, although individuals of any age may be diagnosed with MS.
The estimate of individuals living in the United States with MS is more of an educated guess from experts in the field, versus an exact number of patients. MS organizations have been advocating for several years to create a national MS registry in the United States, but this has yet to become a reality.
In the meantime, the North American Research Committee on Multiple Sclerosis (NARCOMS) has an MS registry with an active database of more than 35,000 individuals with MS. The benefits of a national registry include the ability to learn about the rate of disease diagnosis, progression, and disability, as well as the success of treatments and the availability of services – to better meet the needs of the MS community. If you are interested in learning more or becoming a part of this registry, please visit narcoms.org.
The distribution of this disease is not totally random. On average, with relapsing forms of MS, women are three times more likely than men to develop this disorder. With the primary-progressive form, genders are more equally divided.
Geographically, people who live farther from the equator (in more temperate climates) have a higher risk of developing MS than people living in hotter areas near the equator, or in very cold areas near the north or south poles. Individuals living beyond the 40-degree mark north or south of the equator are far more likely to develop MS, and this is especially true for people in North America, Europe, and southern Australia.
MS is very rare in Inuit populations (sometimes referred to as Eskimos) living in the far north. Asia continues to have a lower incidence of MS. More prevalent among those of northern European or Scandinavian ancestry, Caucasians have a higher incidence than those of African heritage to develop MS.
In addition to the fact that a lower percentage of African-Americans are diagnosed with MS than White-Americans, other differences have been observed. According to recent studies, on average, African-Americans are slightly older at diagnosis, although these statistics can sometimes conflict. Analysis of NARCOMS data shows that a larger proportion of African-Americans have never seen a neurologist who specializes in MS.
African-Americans tend to have more symptoms at the time of diagnosis, which are usually limited to the optic nerves and spinal cord, and this is termed “opticospinal MS.” This means that African-Americans may experience more problems with vision and mobility, versus other common MS symptoms. The disease course tends to be more progressive and responds less to disease-modifying therapies.
A recently published study, however, challenges the existing theories on the prevalence of MS according to race and ethnic background. Appearing in the May 7, 2013 issue of Neurology, the results of this study contradict theories that African-Americans are less prone to MS as compared to Caucasians. The study looked at data from the Kaiser Permanente Southern California health plan (with more than 3.5 million members) from January 1, 2008 to December 31, 2010.
During the timeframe mentioned, 496 individuals were diagnosed with MS. Approximately 70 percent of those diagnosed were women, most of whom were diagnosed with relapsing-remitting MS (RRMS). According to the published results, compared to Caucasians, African-Americans had a 47-percent increased risk of MS, while Hispanics had a 50-percent reduced risk and Asians had an 80-percent reduced risk. The risk of MS was highest for African-American women, whereas the risk of MS for African-American men was lower and about the same as the risk for Caucasian men.
The authors of this study suggest that limitations in earlier studies may have provided inaccurate figures as to the proportion of individuals diagnosed with MS within the different ethnic populations, along with other factors such as misdiagnosis and inadequate medical care. The authors present several possible theories for the results of this study, but in general, explain that their findings “indicate that MS risk is determined by complex interactions among race/ethnicity, sex, environmental factors, and likely genotype.” More studies are needed to confirm the risk of MS among different ethnic populations.
With the help of NARCOMS data, research reveals that Latinos are usually diagnosed at a younger age than both African-American as well as White-American individuals. They tend to have fewer mobility and bladder/bowel problems compared to White-Americans, but may experience more depression. Additionally, research has indicated that fewer Latinos receive access to services to address mental health needs. The same is true for much-needed rehabilitation from specialists in MS, where fewer Latinos are able to access adequate services.
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 situations where one identical twin has been diagnosed with MS, the other twin has a 31-percent risk of developing the disease. (If MS was strictly hereditary, when one identical twin has MS, the other identical twin would have a 100-percent risk of getting MS.) 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. Individuals with MS who smoke also appear to be at a much greater risk of experiencing a more rapid progression of their disease.
Vitamin D as well as exposure to sunlight (both discussed under Possible Causes of MS), appear to reduce the risk of developing MS. The Nurses’ Health Studies (I & II) found that women who were taking 400 IU or more of vitamin D daily had a lower risk of developing MS. Also, populations exposed to greater amounts of sunshine or ultraviolet radiation had lower rates of MS.
Parasites are another possible risk factor in the development of MS. Research has found that parasites can modulate the immune system and dampen its responses. People who have parasites are less likely to be diagnosed with MS, and as conditions in different countries become cleaner – with fewer parasites – the number of individuals being diagnosed is increasing in these parts of the world.
The different patterns of multiple sclerosis affect each person differently. Perhaps you are wondering what MS is going to look like for you, or how the disease is going to progress. Progression is a term that means the accumulation of disability, even when relapses or flare-ups are not present or part of the disease course. Your healthcare provider might use the Expanded Disability Status Scale (EDSS) to measure progression of disability.
Much evidence now suggests that for most patients, progression is slow, and most people with MS do not become severely disabled. Twenty years after diagnosis, about two-thirds of people with MS are likely to still be walking, although some individuals may need assistance with walking. This includes assistive devices to help with mobility, as well as items such as scooters to help conserve energy.
Predicting how fast MS will progress for individual people is difficult, but certain signs and symptoms can provide some clues (a prognosis) about the rate of disease progression. To follow is the clinical and radiologic information that your doctor might consider to predict long-term outcomes, according to studies that have suggested a link between these factors and faster progression. Please note, however, that with the introduction of disease-modifying therapies, as well as new study findings about other risk factors such as smoking, the course of one’s MS may be altered.
- Age: being older than 40 at the time of a first attack
- Male gender
- More than two attacks in the first two years after disease onset
- A score of more than 1.5 on the Expanded Disability Status Scale (EDSS) after the second attack
- Motor symptoms (affecting mobility), or symptoms that affect mental functioning, or symptoms affecting urinary control, at the onset of the disease
- Frequency of relapses (the more relapses you have initially, perhaps the greater the progression of the disease)
- Initial symptoms affecting many parts of the body
- A high number of MRI lesions or lesions in the brainstem at the time of diagnosis
- New or gadolinium-enhancing lesions seen on MRI (these suggest new inflammatory activity)
Other factors may also modify the disease course. These include:
- Racial factors: African Americans who develop MS have a later age of disease onset than Caucasians and are more likely to develop problems with mobility than Caucasians with MS
- Relapsing MS is thought to have a better prognosis than progressive forms of the disease
- Some studies have noted that women with MS who become pregnant have fewer relapses late in pregnancy and an increase in relapses during the three-month postpartum period