(RxWiki News) For many years, researchers have believed that multiple sclerosis (MS) was less common in African Americans than in whites. A new study now questions that long-held belief.
Results from that study showed that the risk of MS was not lower in African Americans than whites. In fact, the risk may even be higher.
However, the higher risk of MS in African Americans was found among women only. African-American women had three times the risk of developing MS compared with African-American men.
"Ask a neurologist about your MS risk."
This study was conducted by Annette Langer-Gould, MD, from Kaiser Permanente Southern California Department of Research & Evaluation in Pasadena, California, and colleagues.
The notion that MS is less common in African Americans than whites can be puzzling when considering that "low vitamin D, which is lower in people with darker skin tones, increases the risk of MS," wrote Dr. Langer-Gould and colleagues.
According to these researchers, the belief that MS is rare in African Americans is based on very limited evidence.
"Our population-based study is the first of its kind to look at this question," said Dr. Langer-Gould in a press statement. "The belief (that African-Americans have a lower risk of developing MS) was based on evidence that was problematic."
So the researchers set out to compare rates of MS between African Americans and whites or Hispanics. They identified 496 patients recently diagnosed with MS, 70.2 percent of whom were women.
The researchers determined patients' race and ethnicity through medical records, health plan administrative records and birth certificates.
Of all the patients in the study, 21.4 percent were African American, 23.4 percent were Hispanic, 2.6 percent were Asian and 52 percent were white.
Study results showed that African Americans had a 47 percent increased risk of MS compared with whites.
Hispanics and Asians, on the other hand, were less likely to develop MS. Hispanics had a 50 percent lower risk than whites and Asians had an 80 percent lower risk.
While the lower risk of MS among Hispanics and Asians applied to both sexes, the higher risk among African Americans was found only in women.
Within each racial/ethnic group, women had a higher risk of MS than their male counterparts, especially African-American women. The risk of MS was 3.11 times higher in African-American women than African-American men. In comparison, the risk of MS was 2.03 times higher in white women, 2.05 times higher in Hispanic women and 1.88 times higher in Asian women than in their male counterparts.
"Our findings do not support the widely accepted assertion that blacks have a lower risk of MS than whites," the study authors concluded.
"A possible explanation for our findings is that people with darker skin tones have lower vitamin D levels and thereby an increased risk of MS, but this would not explain why Hispanics and Asians have a lower risk of MS than whites or why the higher risk of MS among blacks was found only among women," they wrote.
According to Dr. Langer-Gould, "About 19,000 people per year, or 250 people per week, will be diagnosed with MS in the US alone. These numbers highlight the need for more minorities to be included in MS studies, so that we can fully understand how race may play a role in developing the disease."
This study was published in May in the journal Neurology.
The research was supported by the Kaiser Permanente Community Benefits Fund.
Dr. Langer-Gould has been the principal investigator for multiple studies sponsored by pharmaceutical companies. She also has received grant support from the National Institutes of Health (NIH), the National Institute of Neurological Disorders and Stroke and the National MS Society. The other authors declared no conflicts of interest.