Sources of racial disparities in HIV prevalence in men who have sex with men in Atlanta, GA, USA: a modelling study

Abstract

Background In the United States, men who have sex men (MSM) are a most-affected risk group, with Black MSM (BMSM) experiencing markedly higher HIV prevalence than White MSM (WMSM). We created a simulation model to jointly evaluate the strength of existing hypotheses and data in explaining these disparities. Methods A dynamic, stochastic agent-based network model of BMSM and WMSM ages 18-39 in Atlanta incorporated race-specific individual and dyadic-level prevention and risk behaviors, network attributes, and care patterns. We estimated parameters from two Atlanta-based studies of this population (n=1,117), supplemented by the literature. We modeled the ability for racial assortativity to generate or sustain HIV prevalence disparities, alone as well as in conjunction with scenarios of observed racial patterns in behavioral, care, and susceptibility parameters. Findings Race-assortative mixing alone could not sustain a pre-existing disparity. Differences in care cascade, stigma-related behaviors, and CCR5 genotypes each contributed considerably to the disparity, but nearly half (45%) of the disparity remained unexplained. A scenario evaluating race-specific reporting differences was the only one to yield Black HIV prevalence similar to that observed. Interpretation Racial assortativity is an inadequate explanation for observed disparities. Work to close the gap in the care cascade by race is imperative, as are efforts to increase serodiscussion and strengthen relationships among Black MSM especially. Further work is urgently needed to identify other sources and pathways of this disparity, integrate concomitant STI epidemics into models, and understand reasons for racial differences in behavioral reporting. Funding NIH R21HD075662;RC1MD004370;R01MH085600;R01HD067111;R01AI083060; R01HD068395;P30AI027757;P30AI050409;R24HD042828.

Development of an Agent-Based Model to Investigate the Impact of HIV Self-Testing Programs on Men Who Have Sex With Men in Atlanta and Seattle (Preprint)

“…In this paper, we adapted our previous dynamic network-based epidemic model of HIV transmission dynamics [13] and conceptualized and implemented a baseline model as a platform for investigating different HIVST intervention strategies at the individual level. These dynamic network models are ideal for investigating effects of complex, interacting interventions along structured and evolving contact networks [16].…”

“…Our model adapted and extended a previously published dynamic, stochastic, network model of HIV transmission dynamics, which was originally designed to understand racial disparities in HIV among MSM in Atlanta [13]. The original model included key aspects of HIV transmission dynamics among MSM, including the occurrence of condomless anal intercourse (CAI) and related HIV transmission probabilities, sexual partnership characteristics, HIV testing frequency, and HIV care seeking.…”

Addressing Gaps in HIV Preexposure Prophylaxis Care to Reduce Racial Disparities in HIV Incidence in the United States

“…Our prior applications investigated the sources of HIV racial disparities among MSM in Atlanta and the potential impact of PrEP for MSM in the US [30,31]. For this study, we integrated these two research streams to develop the model structure, parameterization, and analyses for simulating PrEP in a race-stratified approach to understand the implications of the PrEP continuum.…”

“…Our model simulates the dynamics of main, casual, and one-time MSM sexual partnerships for non-Hispanic BMSM and WMSM [30,31]. Predictors of partnership formation included partnership type, number of ongoing partnerships (degree), race and age mixing, and sorting by receptive versus insertive sexual position.…”

“…Due to challenges in replicating these values in prior empirical models [30], we incorporated the full 95% confidence intervals of estimated rates of anal intercourse and probabilities of condom use for calibration. We also implemented two race-specific parameters governing the probability of condom failure (due to slippage or breakage), consistently higher in BMSM [43][44][45], and the rate of diagnostic screening for bacterial STIs (increasing the risk of HIV if untreated), often lower for BMSM [4].…”