MS: Rare in African-Americans?

Multiple sclerosis (or MS) is a chronic, often disabling disease that attacks the central nervous system (CNS), which is made up of the brain, spinal cord, and optic nerves.(1) Symptoms may be mild, such as numbness in the limbs, or severe, such as paralysis or loss of vision. The progress, severity, and specific symptoms of MS are unpredictable and vary from one person to another. Today, new treatments and advances in research are giving new hope to people affected by the disease.

MS involves an immune system attack against the central nervous system, specifically the brain, spinal cord, and optic nerves. The disease is thought to be triggered in a genetically susceptible individual by a combination of one or more environmental factors. Although MS is thought by some scientists to be an autoimmine disease, others disagree strongly because the specific target of the immune attack in MS has not yet been identified. For this reason, MS is referred to as an immune-mediated disease.(1)

As the immune system attacks the central nervous system, myelin is damaged, as well as the nerve fibers themselves. Myelin is the fatty substance that surrounds and protects the nerve fibers in the central nervous system. The damaged myelin forms scar tissue (sclerosis), which gives the disease its name. When any part of the myelin sheath or nerve fiber is damaged or destroyed, nerve impulses traveling to and from the brain and spinal cord are distorted or interrupted, producing the variety of symptoms that can occur. Four disease courses have been identified in MS: Relapsing-Remitting MS (RRMS), Primary Progressive MS (PPMS), Secondary-Progressive MS (SPMS), and Progressive-Relapsing MS (PRMS).(2) Physicians evaluate disease progression in four ways: Radiographically—by looking for new lesions, gadolinium-enhanced lesions, or an increased amount of disease on MRI; Electrophysiologically—by measuring changes in the sensory evoked potentials; Neurologically—by measuring changes in function on the neurologic examination; and Functionally—by assessing the person’s physical and cognitive abilities.(2)

MS occurs in most ethnic groups, including African-Americans, Asians and Hispanics/Latinos. It has been thought to be more common in Caucasians of northern European ancestry. Some ethnic groups, such as the Inuit, Aborigines and Maoris, have few if any documented cases of MS regardless of where they live. These variations that occur even within geographic areas with the same climate suggest that geography, ethnicity, and other factors interact in some complex way.(3) Contrary to this commonly accepted belief, African-Americans may have a higher rather than lower risk of developing multiple sclerosis (MS) than Caucasians, according to a new study in the May 7, 2103, print issue of Neurology--the medical journal of the American Academy of Neurology.(4) This population-based study is the first of its kind to look at this question. The belief that African-Americans have a lower risk of developing MS was based on evidence that was problematic, according to the study authors.

The study examined the full database of more than 3.5 million members of the Kaiser Permanente Southern California health plan over a three-year period. They identified 496 people with newly diagnosed MS. This population-based study is thought to be a more accurate way to determine disease risk than to examine only those people who attend a specific clinic or hospital. The study found that African-Americans had a 47 percent increased risk of MS compared with Caucasians, while Hispanics and Asians had a 58 and 80 percent lower risk than Caucasians. Sex differences in MS risk were also emphasized in the study. The higher risk in African-Americans was found in women only whereas the lower risk for Hispanics and Asians was found in both sexes. African-American women had triple the risk of MS compared to African-American men. African-Americans made up 21 percent of those with MS, while they made up only 10 percent of the total study population. Caucasians made up 52 percent of those with MS, compared to 38 percent of the total population. A total of 23 percent of those with MS were Hispanic compared to 40 percent of the total population. Asians made up three percent of those with MS, compared to nine percent of the population. One reason for the study results could be that people with darker skin tones have lower vitamin D levels and ultimately, an increased risk. However, this does not clarify why Hispanics and Asians have a lower risk than Caucasians. About 19,000 people per year, or 250 people per week, will be diagnosed with MS in the U.S. alone. One study demonstrated that African ancestry is a risk factor for a more rapidly disabling disease course.(5) One study’s goal was to create a reference table of disability outcomes in MS that would enable patients to rank their disability relative to others' with similar disease duration and to develop a cost-effective research tool for comparing MS severity across patient populations and time periods.(6) The Disability Expectancy Table allows individual patients to determine how their disability ranks relative to the North American Research Committee on Multiple Sclerosis (NARCOMS) Registry enrollees with the same disease duration. Patient-derived MS Severity Scores (P-MSSS) may be used to compare disability across patient populations and to track disease progression in patient cohorts. P-MSSS does not require a formal neurologic examination and may therefore find wide applicability as a practical and cost-effective outcome measure in epidemiologic studies. There is a need for more minorities to be included in MS studies, in order to appreciate how race may play a role in developing the disease.