HIV incidence in young black gay men in Atlanta, Georgia in the US 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). 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 Atlanta’s Emory School of Public Health, established that lack of health insurance and solely having sexual partners from the black community were almost sufficient as factors, when combined, to explain why incidence in young black men who have sex with men (BMSM) is so much higher than in other MSM. Unemployment and incarceration were also factors that significantly contributed to high incidence.
On the other hand, sexual risk behaviour 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 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 three months. Every three to six 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 in the black men: 44% had HIV compared to 13% of white men. The 562 HIV-negative men were followed-up for two years to determine how many acquired HIV during this period; retention over two 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 US poverty level as opposed to 13% of white men. In addition, they were more likely to identify as bisexual than white men (20% versus 6%) and less as gay (76% versus 92%).
We need to move from observational studies of young men getting infected to stopping them.
Black MSM had higher rates of STIs other than HIV: 28 had rectal gonorrhoea versus 15 white men (2.4 times as many); eight had urethral gonorrhoea versus one white man; and, strikingly, there were 22 cases of syphilis in the black men and none in the white men.
During the study period, there were 24 HIV infections in black men and 8 in white men, yielding an annual incidence of 6.6% and 1.7% respectively. In white men, seven of the eight infections were in men aged over 25: this leads to an incidence estimate of 1.0% in white men under 25 and 1.9% in men 25-39.
In black gay men, the risk relative to age was reversed: there were eight infections in men 25 and older and 16 in men under 25. This yields incidence estimates of 3.5% a year in the older men and 12.1% a year in the younger men.
In univariate 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 it; 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 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 in 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 in 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 four factors entirely accounted for black men’s excess risk of HIV.
Although STIs were so much more common in black men than white men, they were not a highly significant contributor to HIV risk because, nonetheless, only a minority of men had STIs.
A poster (Oster) at the conference also showed that black gay men are much more likely to have partners exclusively of their own ethnicity than other groups. A study by the Centers for Disease Control 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 behaviour 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”.
Rosenberg ES et al. Race and Age Disparities in HIV Incidence and Prevalence Among MSM in Atlanta, GA. 21st Conference on Retroviruses and Opportunistic Infections (CROI), Boston, abstract 38, 2014.
Oster AM 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), Boston, abstract 213, 2014.