- Category: HIV Prevention
- Published on Tuesday, 11 March 2014 00:00
- Written by Gus Cairns
HIV incidence in young black gay men in Atlanta is running at 12.1% a year -- one of the highest figures for HIV incidence ever recorded in a population in the resource-rich world -- according to research presented at the 21st Conference on Retroviruses and Opportunistic Infections (CROI 2014) last week in Boston. Lack of health insurance, incarceration, and partner choice were all implicated as causes.
Only a few studies in resource-poor settings of highly at-risk populations, such as men who have sex with men (MSM) and people who inject drugs, have found higher annual rates of infection. This level of incidence means that a young black gay man becoming sexually active at the age of 18 has a 60% chance of being HIV positive by the age of 30.
The study that uncovered these figures, by researchers at Atlanta’s Emory School of Public Health, established that lack of health insurance and solely having sexual partners from within the black community were almost sufficient as factors, when combined, to explain why incidence among young black men who have sex with men is so much higher than among other MSM. Unemployment and incarceration were also factors that significantly contributed to high incidence.
On the other hand, sexual risk behavior did not contribute because, as some other studies have found, young black gay men actually have lower rates of unprotected anal sex than white men. In addition, this survey did not find that age-mixing -- tending to have sex with partners significantly younger or older than oneself -- was a factor in high incidence, contrary to what some other studies have found.
The InvolveMENt Study
InvolveMENt was a longitudinal cohort of black and white HIV negative MSM aged 18 to 39, recruited at gay venues and meeting places and on Facebook. Only men self-defining as "black" or "white" were included; Hispanic, mixed-race, and other ethnicities were excluded, as the idea of the study was to draw a contrast between the risks faced by black and white gay men.
The only other criterion for eligibility was to have had any sex with a man in the past 3 months. Every 3 to 6 months, participants had an HIV test and completed surveys about their own and their partners’ risk factors.
InvolveMENt recruited 803 men, 56% of them black. At baseline, HIV prevalence was already much higher among the black men: 44% had HIV compared to 13% of white men. The 562 HIV negative men were followed-up for 2 years to determine how many acquired HIV during this period; retention over 2 years was 79%, yielding 832 person-years of data.
Looking solely at the HIV negative men (260 black and 302 white), there were significant differences between them. Half the black men were under 25 compared with a third of the white men; 24% had no college education compared with 11% of white men; 54% had health insurance compared to 76% of white men; and 29% had incomes below the U.S. poverty level compared to 13% of white men. In addition, black men were more likely than white men to identify as bisexual (20% vs 6%) and less as gay (76% vs 92%).
Black MSM had higher rates of sexually transmitted infections (STIs) other than HIV: 28 had rectal gonorrhea versus 15 white men (2.4 times as many); 8 had urethral gonorrhea versus 1 white man; and, strikingly, there were 22 cases of syphilis among the black men and none among the white men.
During the study period there were 24 HIV infections among black men and 8 among white men, yielding annual incidence rates of 6.6% and 1.7% respectively.
Among white men, 7 of the 8 infections were in men age 25 or older. This leads to an incidence estimate of 1.0% per year for white men under 25 and 1.9% for men age 25-39.
Among black gay men, the risk relative to age was reversed: there were 8 infections in men age 25 or older and 16 in men under 25. This yields incidence estimates of 3.5% per year for the older men and 12.1% for the younger men.
In a univariate or sigle-factor analysis, black men in general were 3.8 times more likely to acquire HIV but, more strikingly, men who had black partners were 4.5 times more likely to acquire the virus. In other words, who comprised a man's sexual network was even more important than his own individual characteristics.
Men with no health insurance were 2.4 times more likely to become HIV positive. In addition, having unprotected sex, unsurprisingly, multiplied the risk of HIV acquisition 4.8 times and, for the group as a whole, having had partners at least 10 years older multiplied the risk 2.8 times.
The investigators did a multivariate or multi-factor analysis to find out what factors might explain higher HIV incidence in black men. In this analysis, black men had 2.9 times the HIV risk of white men.
The researchers selected a risk factor and calculated by how much black men’s incidence would still exceed white men’s if this risk factor was adjusted to the mean for the whole cohort. For instance, they found that if the rate of unprotected sex among black men was the same as the average rate for the whole cohort, their risk of HIV would actually rise to 3.3 times the risk in white men: this was because black men were actually having less unprotected sex, and this acted to some degree as a moderating factor.
The network effect was by far the strongest factor. If black men selected their sexual partners from black or white men randomly, it was found, their risk would fall to 1.6 times the risk in white men, which would no longer be a statistically significant excess. If health insurance was added to this, it would reduce the excess risk to 1.5 times the risk for white men.
Although analysis of these factors was not presented, presenter Eli Rosenberg said that if incarceration and unemployment were added into the mix, then taken together these 4 factors entirely accounted for black men’s excess risk of HIV.
Although STIs were much more common among black men compared to white men, they were not a highly significant contributor to HIV risk because, nonetheless, only a minority of men had STIs.
A poster at the conference (abstract 2130) also showed that black gay men are much more likely to have partners exclusively of their own race/ethnicity than other groups. A study by the Centers for Disease Control and Prevention (CDC) found that 63% of black MSM's sexual partners were black; in contrast 47% of white men’s partners were also white, 27% of Hispanic men’s partners were Hispanic, and only 8% of Asian men’s partners were Asian.
The extreme concentration of HIV in the black gay population -- and especially the feeling that behavior change and safer sex were clearly not sufficient to control risk -- caused some comments in the audience. "We need to move from observational studies of young men getting infected to stopping them," said one commenter. "We need to push pharmaceutical companies into marketing PrEP for this group," referring to pre-exposure prophylaxis, or taking antiretroviral drugs to prevent HIV transmission.
ES Rosenberg, PS Sullivan, CF Kelly, et al. Race and Age Disparities in HIV Incidence and Prevalence Among MSM in Atlanta, GA. 21st Conference on Retroviruses and Opportunistic Infections (CROI 2014). Boston, March 3-6. Abstract 38.
AM Oster, JO Wertheim, AL Hernandez, et al. HIV Transmission in the United States: The Roles of Risk Group, Race/Ethnicity, and Geography. 21st Conference on Retroviruses and Opportunistic Infections (CROI 2014). Boston, March 3-6. Abstract 213.