Differentiating the associations of binge (5+ drinks) and social (1-4 drinks) alcohol use with event-level sexual risk behavior by HIV-status among substance-using MSM

Background: Men who have sex with men (MSM) continue to be at high risk for HIV infection. Differentiation between social (1-4 drinks) and binge (5+ drinks) alcohol use is needed to better understand the potential dose-related association of alcohol and risk behavior at the sexual event level. Methods: We analyzed data from 1206 substance-using MSM randomized into Project MIX, a multisite HIV prevention intervention trial in Chicago, Los Angeles, New York, and San Francisco (2005-06). Multivariate analysis focused on event-level substance use and sexual behavior during respondents' most recent anal sex encounter. Results: Among HIV-negative men (n=599), 30% reported binge drinking, 27% reported social drinking, and 43% reported no alcohol use during their last anal sex encounter; 27% had unprotected receptive anal (URA) and 39% had unprotected insertive anal (UIA) sex during the encounter. Controlling for other drug use and demographic variables, binge drinking was associated with URA (OR=2.02, CI=1.29-3.15) but social drinking was not (p>.05). Alternatively, social drinking was associated with UIA (OR=1.54, CI=1.01-2.34) but binge drinking was not (p>.05). HIV-positive men (n=607) also reported binge drinking (22%), social drinking (32%), and no alcohol use (22%) during their last sex encounter. Binge or social drinking were not significantly associated with URA or UIA (p>.05). Conclusions: Social and binge drinking have differential associations with sexual risk behavior – especially for HIV-negative MSM. Future HIV prevention and research should assess for social and binge drinking in order to better understand and address the nuanced links of alcohol use and sexual risk.