Correlates of group sex participation among cisgender men who have sex with men in Seattle, WA.

BACKGROUND: Group sex events (GSEs) have potential implications for transmission and acquisition of HIV and sexually transmitted infections (STI). METHODS: We analyzed survey data from Project DETECT, a Centers for Disease Control and Prevention-funded study evaluating point-of-care tests. Our analytical sample included cisgender gay, bisexual, and other men who have sex with men (cisGBMSM) seeking HIV/STI testing who reported at least one anal sex partner in the past three months. We defined recent GSE as a sexual encounter in the past three months involving more than two people. Poisson regression compared demographic characteristics and behaviors between participants and partners of participants who reported GSE participation vs. ≥2 sex partners but no recent GSEs. RESULTS: Recent GSE was reported at 707 (36%) of 1,991 study visits by 1,539 unique participants. Participants who reported bacterial STI diagnosis in the past three months (PR=1.31, 95%CI=1.16-1.49) and current pre-exposure prophylaxis (PrEP) use (PR=1.49, 95%CI=1.32-1.69) were more likely to report a GSE than to report ≥2 sex partners and no GSE. Partners recently diagnosed with an STI (PR=1.21, 95%CI=1.06-1.37) and partners with other concurrent partners (PR=1.91, 95%CI=1.62-2.26) were more likely to be partners of participants who reported GSE than participants with ≥2 partners but no GSE. CONCLUSIONS: GSE participation was common among cisGBMSM. While GSE participation was associated with some predictors of HIV infection, GSE participants were more likely to use PrEP. Healthcare for cisGBMSM should include assessing GSE participation and discussing strategies for HIV/STI prevention in the context of GSE.