This cohort
study with young men who have sex with men (YMSM) in Chicago explored the effects of
networks on HIV transmission in order to explain the racial disparities in HIV
rates among MSM in the US. As well as individual factors, the authors took a
network approach, involving measures of sexual connectedness within networks
which could possibly account for higher HIV rates among black YMSM. Factors
such as homophily (the likelihood of having a same-race sexual partner) and
density of networks may play a crucial role in HIV transmission.
Researchers
used community sampling, drawing on partner and peer connections when
recruiting participants. All of the 1015 participants were aged 16-29, with 34%
identifying as black, 30% as Latino, 25% as white and 11% as other. Of the
cohort, 49% indicated some college education, with a higher percentage of white
MSM indicating this (59%).
A higher
percentage of black MSM indicated bisexuality as a sexual preference when
compared with white MSM (26% vs 10%). There was a much larger percentage of
HIV-positive black MSM (32%) than either Latino (13%) or white MSM (2%) in the
cohort.
Networks
were generated by asking each participant to indicate individuals who were
known to them socially, sexually or as people they took drugs with. Once the
participant named five network members, information was gathered regarding
demographics, characteristics of the relationship and interactions between the
participant and the network members. For sexual partners, detailed information
was obtained, including frequency of sexual contact, condom use and so forth.
Sexual
connectedness within a network was measured by measuring three attributes:
- Homophily: the degree of sexual preference you
have for people of your own ‘type’ (in this case, race).
- Transitivity: the average number of sex ties
between network members.
- Density: the ratio of sex ties between members
in a network out of all the possible sex ties that could exist.
Black MSM
were found to have high levels of density and racial homophily, but low
transitivity. In other words, black men were more likely to have sex only with
men and women of their own race than white men; they were more likely to have
sex with more of the people they did know; but they were less likely to have
sex with people who also had sex with each other.
Black MSM
also reported a larger number of sexual partners who were female, transgender
or did not identify as gay.
At the
individual level, results show that there were racial differences in terms of
substance abuse and psychological symptoms: black men were more likely to use
cannabis, with white men significantly more likely to report alcohol abuse.
Depression scores were significantly higher for white MSM than for black MSM,
whereas suicide attempts were more common among black MSM than white MSM.
There were
significant racial differences in risk-taking behaviour, with black MSM
reporting the lowest number of sexual partners and engaging in less condomless
sex. Black MSM reported experiencing significantly higher stigma (both
externalised and internalised) than either white or Latino MSM.
Biologically,
in addition to higher HIV rates, and more likelihood of detectable viral loads
among HIV-positive black MSM (61% vs 20% for white MSM), higher rates of
rectal STIs were also observed in black men.
At a
structural level, for those who were HIV positive, there were no racial
differences regarding the number of missed antiretroviral doses and number of
visits to healthcare practitioners. However, the authors did not comment on
health insurance differences between racial groups or the proportion of black
HIV-positive men on treatment. Additionally, there were only five HIV-positive
white men in the study – this small sample may not reveal significant structural
differences between the racial groups.
Despite
higher HIV infection rates, black YMSM reported more lifetime HIV tests. There
were no differences observed among the racial groups when looking at pre-exposure prophylaxis (PrEP) use
in the last six months. Black YMSM reported significantly more violence
and trauma with childhood sexual abuse experienced by 32% compared to 14% for young
white MSM.
These
results indicate important multilevel differences that may account for racial
disparities in HIV infection rates. The network findings suggest that black
YMSM are exposed to HIV infection via fewer pathways but engage in more sexual
contact with other network members. Thus, even though the total number of
partnerships may be lower, the high density creates more opportunity for HIV
exposure from repeat encounters.
This
research emphasises the importance of interventions that directly address social
determinants such as stigma and victimisation, while also accounting for
network trends. Future interventions may have greater success at reducing racial
infection disparities by addressing not only individual level factors, but also
working at the structural and network levels to prevent infection.