Engagement in group sex among geosocial networking mobile application-using men who have sex with men.

BACKGROUND Men who have sex with men (MSM) remain the group most affected by the HIV epidemic in the United States. At least one-quarter of MSM report engagement in group sex events (GSEs), which can pose a risk for HIV transmission and acquisition. In this study, identification of event-level correlates of sexual and drug use behaviours at GSEs was sought to better inform prevention activities. METHODS For this study, participants were recruited via banner and pop-up advertisements placed on a geosocial networking mobile phone application that MSM use to meet men. RESULTS Of the 1997 individuals who completed the study screener, 36.0% reported participating in at least one GSE in the prior year. In multivariable logistic regression analysis, attendance at a GSE in the past year was significantly associated with older age, full/part time employment and being HIV positive. Of the men who attended a GSE, more than half reported condomless anal sex (CAS) with at least one of their partners (insertive: 57.7%; receptive: 56.3%). MSM who indicated drug use had significantly higher odds of having insertive CAS [odds ratio (OR)=2.45; 95% confidence interval (CI): 1.37-4.39] and receptive CAS (OR=3.60; 95% CI: 1.96-6.63) at their last GSE. CONCLUSIONS The high prevalence of HIV-positive MSM engaging in group sex, coupled with their greater odds of CAS, poses a significant risk for HIV/STI transmission within the group sex setting. More research is needed to determine patterns of condom use at these events and whether seroadaptive behaviours are driving CAS.