We've all seen the statistics showing that black MSM are more likely to become HIV positive than white MSM. According to the Centers for Disease Control and Prevention, in 2015 the rate of HIV diagnoses for black men was nearly eight times the rate among white men.
However, the reason for the disparity is not so clear. In a study of 18- to 39-year-old MSM in Atlanta, published in April 2017 in the British medical journal The Lancet, researchers examined common theories.
Many studies have attempted to explain the higher rates of HIV diagnosis among black men by isolating variables. For example, one study might examine the effect of stigma's greater impact on black men, while another might look at how blacks traditionally have had less access than whites to high-quality health care.
Rather than focus on one particular factor at a time, researchers created a simulation model that combined the data from multiple studies and examined how much of an impact each factor had -- sexual networks, sexual behaviors, disclosure, the HIV care continuum (also called the treatment cascade) and genetics among them. The researchers selected Atlanta because approximately 10 percent of HIV diagnoses among black gay and bisexual men occur there.
Explaining the Unexplained?
One of the study's biggest findings was that we have a lot more to learn. Researchers found that the factors accounted for, at most, 55.5 percent of the racial disparities in HIV prevalence that have been observed thus far.
Take race-assortative mixing, which refers to the tendency of people to have sex within networks made up of those of their own race. A common theory has been that this is one of the reasons for the continuing higher incidence of HIV among black MSM: black MSM are more likely to have sex with other black MSM, so the higher incidence of HIV in the black community will perpetuate itself indefinitely. But The Lancet study "debunked" what study co-author Eli S. Rosenberg, Ph.D., calls "a pretty common narrative." In fact, the researchers' simulations suggest that the differences in HIV rates between black and white communities would narrow over time, says Rosenberg, an assistant professor of epidemiology at Emory University's Rollins School of Public Health.
The finding undermines the notion that sex between members of the black community is inherently higher risk -- a belief that Rosenberg believes stigmatizes both black men and black communities. "I think that's really important to de-escalate a very loaded viewpoint, like [the] set of work that says that black communities are inherently risky," he says.
The researchers also examined behaviors that could be driven by stigma. A number of studies have shown that black MSM feel less comfortable disclosing their HIV status with their partners because of stigma, and that, too, could put their partners at greater risk.
In addition, researchers considered the effect of disparities on the HIV care continuum. In the United States, blacks are less likely than whites to have access to HIV care and treatment, which means that they are less likely to be in treatment if they have HIV, and their viral load is less likely to be suppressed. That could put their sexual partners more at risk.
The study also looked at biological reasons for the racial disparities. Studies have shown that some people who appear to be resistant to HIV have a mutation of the CCR5 protein in their bodies, called the CCR5D32, or CCR5-delta 32, mutation. However, this mutation is more prevalent in those of European ancestry.
Even with these and other factors accounted for, the study researchers found that 44.5 percent of factors resulting in HIV disparities between black and white gay and bisexual men remain unexplained.
A Starting Point
A major takeaway from the study is how little we actually know, says Kenyon Farrow, U.S. and global health policy director for New York-based research and policy think tank Treatment Action Group: "We still don't really have a good grasp on why the disparity exists for black gay men. There's still a huge chunk of related factors that are just unknown."
There is also a need for research that shows which solutions can bring about the best results, Farrow says: "We need more research to help us actually get to policy, programs and health care infrastructure that help us actually address the problem."
Some of the study's findings, however, can provide a starting point. For example, the study found that just under one-quarter of the disparity is attributable to discrepancies in HIV care. That provides a plan of action: If we can improve care in African American communities, we may see fewer new infections in the population.
Some of the factors can't be controlled, such as the CCR5-delta 32 mutation. "But [the mutation] explains less than 20 percent of the disparity, which means that 80 percent or more of the disparity is probably actionable in some way," says study co-author Steven M. Goodreau, Ph.D., associate professor of anthropology at the University of Washington.
Tamara E. Holmes is a Washington, D.C.-based journalist who writes about health, wealth and personal growth.
[Note from TheBody.com: This article was originally published by The Black AIDS Institute on Aug. 1, 2017. We have cross-posted it with their permission.]