Treating MS – does ethnicity matter?
Multiple sclerosis is considered to be a disease that largely affects whites of European ancestry. The proportion of people with MS who are non-white hasn’t been determined, and comparatively little is known about MS in these people.
What is known is that when MS does strike people of non-white ethnicity, the effects can be severe. MS is generally worse in African-Americans and Hispanics, (Ventura and colleagues. Mult Scler 2016; epublished November 29, 2016), and African-Americans are less likely to have a benign course (i.e. not develop significant disability over the long term) compared to white Americans (Zivadinov and colleagues. BMC Neurol 2016;16:102).
MS symptoms are also slightly different. In an analysis of people with early MS, the most common initial symptom was transverse myelitis (which affects walking ability) in African-Americans, and optic neuritis (affecting vision) and seizures in Hispanics, symptoms which can be very disabling early on (Langer-Gould and colleagues. J Neurol 2014;261:1349-1355; Langille and colleagues. J Child Neurol 2016;31:1068-1073). African-Americans also suffer more nerve damage, as shown by early deterioration in the retinal nerve (a marker of tissue loss in the brain), and by more extensive tissue loss in grey-matter structures in the brain (Seraji-Bororgzad and colleagues. Mult Scler Relat Disord 2016;7:16-20; Al-Kawaz and colleagues. J Neuroimaging 2016; epublished September 16, 2016).
One notion that has come under fire in recent years is that MS is rare among African-Americans. A database analysis of people in California found that the incidence (i.e. the number of new cases in a given time period) was highest among African-Americans (10 cases per 100,000 population) and whites (about 7 cases/100,000), and lowest among those with Hispanic (about 3/100,000) or Asian (about 1/100,000) ancestry (Langer-Gould and colleagues. Neurology 2013;80:1734-1739). This higher MS risk among African-Americans was due entirely to the high rate of MS among African-American women – about 60% higher than in white women. The rate of MS was comparable between African-American and white men.
The emphasis on MS as a Northern European disease has had three main consequences. The first is the problem of self-fulfillment – physicians may not expect to see MS in non-whites, so they may be less likely to diagnose it, and people may suffer delays in getting treatment.
Secondly, few non-whites are enrolled in treatment trials – a problem that would appear to be getting worse (Avasarala J. JAMA Neurol 2014;71:943-944). For example, about 6-7% of subjects in early clinical trials of interferons (Avonex, Betaseron, Rebif) and Copaxone were non-white. A similar proportion was seen in the TRANSFORMS trial of Gilenya. But the proportion of non-whites has dropped considerably in more recent studies – 3% in the TEMSO trial of teriflunomide, and only 2% in the DEFINE trial of Tecfidera.
As a result, little is known about the effectiveness of MS medications in non-white populations. A few studies have tried to determine if MS medications are as effective in blacks and Hispanics. One study found that African-Americans appeared to be less responsive to interferons, experiencing more relapses and brain lesions on their MRI, compared to white Americans (Cree and colleagues. Arch Neurol 2005;62:1681-1683). However, the study was hampered by the very small number of African-Americans, who represented only 6% of the 652 people in the study.
Tysabri did appear to be effective in African-Americans, reducing the relapse rate by 60% and the number of new MRI lesions by 79% (Cree and colleagues. Arch Neurol 2011;68:464-468). More recently, a large study at two MS centres in the U.S. found that Tecfidera was just as effective in African-Americans and Hispanic Americans as it was in white Americans (Zhovtis Ryerson and colleagues. Ther Adv Neurol Disord 2016;9:454-461).
These findings indicate that people of various ethnicities can obtain the same benefit from treatment as others, but a higher-efficacy therapy may be necessary to gain a better measure of control over the disease process.
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