Variations in Sexual Behaviors by Use of Specific Substances Among Vancouver Gay, Bisexual, and Other Men Who Have Sex with Men: An Event-Level Analysis.

Event-level studies measure substance use and sexual behaviors happening during a specific sexual encounter, ensuring that both variables are temporally paired. This study explored the event-level associations between a range of sexual behaviors (masturbation, anal sex, oral sex, rimming, fisting, sex toys, and group sex) and five sexualized substances (poppers, methamphetamine, GHB, ecstasy/MDMA, and ketamine) used during 11,582 sexual events reported by 762 gay, bisexual, and other men who have sex with men (GBMSM) in Vancouver, Canada. Data were obtained from a prospective cohort of GBMSM who self-reported their behaviors via computer-based questionnaires on their last sexual encounter with up to five of their most recent partners in the past six months. These clustered data were analyzed with multivariable generalized linear mixed models. Participants reported popper use in 16.1% of sexual encounters, methamphetamine in 8.6%, gamma-hydroxybutyrate (GHB) in 4.1%, ecstasy/3,4-methylenedioxymethamphetamine (MDMA) in 3.3%, and ketamine in 1.5%. Condomless receptive anal sex (25.0% of events) was associated with increased odds of using poppers, methamphetamine, GHB, and ecstasy/MDMA. Group sex (13.1% of events) and sharing sex toys (2.0% of events) were more likely with the use of all five substances. Receiving money/drugs/goods in exchange for sex (2.5% of events) was associated with increased odds of poppers, methamphetamine, GHB, and ecstasy/MDMA use. GBMSM living with HIV (29.9% of participants) had higher odds of using poppers, methamphetamine, and GHB, but lower odds of using ecstasy/MDMA. In conclusion, these event-level results suggest public health strategies are needed to address the possible negative impacts of sexualized substance use among GBMSM.