DALLAS – There is a need for prospective, multicenter studies to examine the differences between African Americans and whites with multiple sclerosis and their response to therapy, according to Dr. Omar Khan.
The impact of education, disease awareness, and access to health care as covariates must also be included in future studies, "otherwise, this question will continue to come up, to find out whether these factors do or don’t have a bearing on disease severity and outcomes," said Dr. Khan, professor and chair of neurology at Wayne State University, Detroit, during a presentation at a meeting of the Consortium of Multiple Sclerosis Centers and the Americas Committee for Treatment and Research in Multiple Sclerosis.
Another point to consider, especially in regard to trials evaluating response to disease-modifying therapies, is that African Americans continue to be a small proportion of participants in these trials, he said.
Up until recent decades, it was believed that multiple sclerosis didn’t affect African Americans. Even today, some resources, such as the National MS Society's website, try to bust that myth first before delving into other facts about multiple sclerosis.
Nearly 10 years ago, Dr. Bruce Cree and his colleagues presented a study about the clinical characteristics of multiple sclerosis in African Americans, compared with whites, and they showed that African American patients were more likely to have a more aggressive disease course, and a greater likelihood of developing opticospinal MS and transverse myelitis (Neurology 2004;63:2039-45).
The study showed that the median time from onset to diagnosis was 1 year in African Americans, compared with 2 years in whites. Also, the median time from onset to treatment was 4 years in African American patients, compared with 5 years in whites. The former group also had a significantly shorter median time to a Kurtzke Expanded Disability Status Scale (EDSS) score of greater than or equal to 6 and 7, compared with whites.
These findings have been consistently shown in later trials.
In 2004, a group in France showed that the MS course was more aggressive in North African than in European patients (Neurology 2007;68:29-32). Researchers found that the mean age of onset was younger in North Africans, compared with Europeans. They also found that the median times to EDSS scores of 4 and 6 were both significantly shorter in the former group.
"You’re going to see this theme in other studies," said Dr. Khan. "Clearly there wasn’t a delay in diagnosing the disease based on these studies."
Then in 2008, a study in France showed that North African migrants with MS appear to be as responsive as other MS patients are to disease-modifying therapies, although they received the treatment sooner than their white counterparts and had more frequent use of immunosuppressive drugs (Mult. Scler. 2008;14:933-9). The study showed that the mean time to an EDSS score of 6 was 6 years in North Africans, which was almost 10 years sooner than in white patients.
In 2009, in a retrospective study of pediatric-onset MS, Dr. Khan and his colleagues yet again found "a more aggressive disease phenotype among American blacks with adult-onset MS," and called for larger multicenter studies, which Dr. Khan continues to advocate for (Pediatr. Neurol. 2009;40:31-3). The group found an earlier onset of disease to initiation of disease-modifying therapy among African American patients, compared with whites, although the difference didn’t reach statistical significance. The relapse rate was also higher among the former group.
Another study on pediatric-onset MS showed that African American patients may be at higher risk for adverse cognitive impact on language and complex attention (Neurology 2010;75:2097-102).
Dr. Khan also pointed to several studies quantifying central nervous system tissue injury in African Americans with MS.
A 2012 study showed that African Americans had a significantly greater lesion volume, compared with white patients, but the brain volumes weren’t significantly different between the two groups. Researchers concluded that "a higher lesion accumulation, rather than a pronounced brain volume decrease, might explain the early progress to ambulatory assistance of [African Americans] with MS" (PLoS One 2012;7:e43061).
"I don’t think we should be arguing that there is a clear indication that African Americans have greater disability, CNS tissue injury, and possibly suboptimal response to therapy," compared with whites, Dr. Khan said.
Other quantitative studies have suggested differences in the disease biology. "And they provide more credence to these observations, despite the fact that almost all of them have been cross-sectional or retrospective," he said, stressing the need for prospectively designed multicenter studies.
"And I think it’s equally important to keep in mind [that] the impact of education, health awareness, and access to health care as covariates at a bare minimum must be included in these studies," Dr. Khan said.