July 26, 2012
Behavioral Factors Don't Explain Disproportionate HIV Epidemic Among Black MSM
by Tim Horn
Black men who have sex with men (MSM) are significantly more likely to become infected with HIV compared with non-black MSM, yet they are less likely to engage in many risky behaviors. This is the paradoxical finding of a critical review of nearly 200 studies reported by Gregorio Millet, MPH, of the U.S. Centers for Disease Control and Prevention (CDC) and his colleagues on Tuesday, July 24, at the XIX International AIDS Conference (AIDS 2012) in Washington, DC, and published in a special supplement of The Lancet.
One of the most striking HIV infection imbalances in the United States involves black MSM. Though they represent less than 1 percent of the entire U.S. population, nearly a quarter of all new HIV infection in 2009 were in black MSM. And according to CDC surveillance data, HIV cases increased by an astonishing 48 percent in young black MSM between 2006 and 2009.
To make some sense of the highly disproportionate HIV incidence and prevalence among black MSM, compared with other MSM, Millett’s group analyzed data from 194 studies; seven conducted in Canada, 13 conducted in the United Kingdom and 174 conducted in the U.S. The researchers looked at 69 known risk factors for HIV in the studies, which included a total of 106,000 black MSM and more than a half-million MSM of other races/ethnicities.
Confirming CDC estimates, Millett noted that black MSM were three times as likely to have tested positive compared with their non-black MSM counterparts. They were also six times as likely to have another sexually transmitted infection (STI).
Paradoxically, however, very few of the often-cited behavioral risk factors explained these discrepancies.
Black MSM were somewhat less likely to engage in unprotected anal intercourse with male partners than other MSM, Millett reported. They were also no more likely to engage in unprotected receptive anal intercourse than other MSM. Black MSM were also less likely to have a high number of lifetime male sex partners or a high number of male partners within the year prior to completing surveys or questionnaires in their respective studies.
Black MSM were also more than two times as likely to use condoms and were 50 percent more likely to have been tested for HIV within the previous 12 months. They were also more likely to have been tested for the virus more than once.
Differences in illicit substance use did not explain the higher HIV rate among black MSM. In fact, compared with MSM of other races/ethnicities, black MSM were less likely to have used drugs at any point in their lifetimes or in the months prior to their study participation. Sepcifically, black MSM were less likely to have used alcohol, marijuana, injection drugs or amphetamines, and were less likely to have used any drug before or during sex. Crack cocaine use proved to be the only drug linked more closely to black MSM than other MSM.
So which risk factors did potentially explain the tremendous disconnect? Many, Millett noted, were related to socioeconomic and access-to-care disparities.
Black MSM were significantly more likely to have a current sexually transmitted infection. They were also less likely to have finished high school and more likely to have been incarcerated, to have a low income and to be unemployed.
HIV-positive black MSM in the analysis were more likely to have undiagnosed HIV infection, to have a CD4 cell count below 200, to have no health insurance coverage, to have limited access to ARV therapy, and, in cases where ARVs were prescribed, less adherent to their dosing schedules. Black MSM were also less likely to have undetectable viral loads and were less likely to see their health care providers regularly.
In other words, HIV-negative black MSM may be less likely to engage in risky behaviors, but if they do engage in unprotected anal intercourse, they may be more likely to do so with a highly infectious partner—for example, an HIV-positive black man who does not know he is infected or receiving the care and support he needs to get his viral load undetectable. Another study presented at the conference explored this particular scenario.
With regard to another potentially important disparity—that black MSM are more likely to engage in sexual activity with older MSM—Millett’s group strongly urged increased efforts to diagnose and treat older MSM (those 30 years of age and older) to help stem increasing rates of new infections in young black MSM.
“A clear and paradoxical pattern of similar or less risk behavior and risk of HIV or STIs emerged in [the analysis],” Millett and his colleagues concluded.
“HIV epidemics in black MSM are inextricably linked to social and economic environments that should be considered and addressed to successfully stem disparities in HIV infection,” Millett and his colleagues added. “Interventions that support early initiation of ARV therapy, adherence and clinical visits for HIV-positive black MSM might have a greater effect in the reduction of HIV infection rates than do those that focus on sexual or drug use risks.”
Editor's postscript: A number of comments in response to this article argue that the differences noted in risk behaviors and HIV infection between black MSM and MSM of other races/ethnicities could be due to reporting bias—untruthful responses to questioning—and that black MSM may be under-reporting their risk behavior. Millett and his colleagues noted, however, that other studies have failed to find differences in reporting of risk behavior between black and other MSM. Moreover, Millett and his colleagues noted, the fact that the same pattern (less risk and greater HIV infection) is evident across studies with different mothods, samples of black MSM, and regions of a country (not to mention different countries), along with consistent data collected from 1987 to 2011, arguments pointing to a higher likelihood of bias and under-reporting become less credible.
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