MS Incidence Higher in Blacks?

May 07, 2013

New results have suggested for the first time that multiple sclerosis (MS) may actually affect the black population more than whites.

"We found a very striking difference in women — MS was a lot more prevalent in black women than in white women," lead author of the study, Annette Langer-Gould, MD, PhD, Kaiser Permanente Southern California, Pasadena, commented to Medscape Medical News. "Whether this has always been the case or if something has changed recently we don't know."

She added, "Many doctors will think this is a surprising finding as it has always been believed that MS was a white person's disorder. But I think our results will confirm what a lot of physicians in the south of the United States are already seeing — that black people do get MS."

However, the study has confirmed that MS affects women more than men, with around 70% of cases occurring in women.

From their results, the researchers also estimate that MS will be newly diagnosed in approximately 19,000 individuals per year or 250 per week in the United States alone.

Their findings are published in the May 7 issue of Neurology.

250 New Cases per Week

For the study, Dr. Langer-Gould and colleagues used the complete electronic medical records covering more than 9 million person-years of observation from the multiethnic, community-dwelling members of the Kaiser Permanente Southern California health plan from 2008 to 2010. They searched for the code for MS and extracted medical records to confirm the diagnosis and obtain race or ethnicity data.

They identified 496 patients with newly diagnosed MS. The average age at diagnosis was 41.6 years, and 70.2% of patients were women. Results showed that the incidence of MS was higher in blacks, and lower in Hispanics and Asians, than in whites.

In addition, the female preponderance was more pronounced among black (79.3%) than white, Hispanic, and Asian individuals with MS (67.8%, 68.1%, and 69.2%, respectively; P = .03).

Table 1. Incidence of MS by Race

Group Incidence of MS per 100,000 Person-Years MS Cases in Women (%)
Black 10.24 79.3
White 6.94 67.8
Hispanic 2.94 68.1
Asian 1.39 69.2

 

Black women had a higher risk for MS than white women, whereas black men had a similar risk for MS compared with white men.

Table 2. Risk for MS by Race and Sex

Group Risk Ratio for MS in Blacks vs Whites (95% Confidence Interval)
Women 1.59 (1.27 - 1.99)
Men 1.04 (0.67 - 1.57)

 

Dr. Langer-Gould noted that there were still more white patients with MS in total in this study because there are more white people in southern California, but there is a higher incidence in the black population.

"Our study suggests that when whites and blacks live in the same community, there is a higher incidence of MS in blacks."

"Not Just a Disease of White People"

She said this study should taken as a cautionary tale. "Before we start assuming things — ie, that MS is mainly just a disease of white people — we should look more closely at the evidence. I think it is likely that until now the right study hadn't been done."

She explained that the assumption that MS affected manly white people was based on 1 study of male veterans in the 1950s, which found that white men were twice as likely to be claiming a particular benefit for MS as black men.

"But at that time, it may have been that white men were more able to navigate the complexities involved in claiming benefits, so it doesn't really tell us definitively that whites have a higher incidence of MS than blacks. And it was done in men only." Dr. Langer-Gould noted that this study was recently repeated and found similar results for white and black men.

She suggested another reason that MS may have been considered a disease of the white population is that it tends to occur more frequently in countries farther away from the equator, where typically more white people live. "But black people are now starting to settle in areas that were once traditionally white and we are starting to see that MS does affect black people too, perhaps more so than whites."

She added that it is possible that in Africa, many MS cases may go undiagnosed. "It is not an easy diagnosis to make, especially in area where there is a high level of infection, which can mimic some of the symptoms. The diagnosis needs an MRI brain scan and a neurologist and these are not readily available in Africa."

Dr. Langer-Gould's team is now conducting a second study, known as the MS Sunshine study, to understand more about the cause of MS.

"We want to look at various factors that we think may be involved — sunlight, vitamin D, lifestyle factors such as smoking, obesity, or genetic factors," she said. "This is a case-control study in newly diagnosed MS patients who will be matched with controls."

This study was funded by Kaiser Permanente Community Benefits Fund. Dr. Langer-Gould is site principal investigator for several phase 3 clinical trials sponsored by Biogen and Roche.

Neurology. 2013;80:1734-1739. Abstract

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