Patterns of Event-Level Concurrent Substance Use During Sex Among Gay, Bisexual, and Other Men Who Have Sex with Men in Metro Vancouver.

This study identified patterns of sexualized substance use among gay, bisexual, and other men who have sex with men (gbMSM) and examined associated risk factors for sexually transmitted and blood borne infections (STBBI). Data were from a longitudinal cohort recruited using respondent-driven sampling between Feb-2017 and Feb-2019. Participants reported on events with up to five of their most recent sexual partners. Latent class analysis examined patterns of concurrent substance use 2 h prior to or during sex. Multinomial regression identified demographic, partner-level, and event-level factors associated across 11,877 sexual events reported by 757 participants. Most combinations of substance use were rare, but most drugs were frequently combined with other drugs when they were used prior to or during a sexual event. Six latent classes of concurrent event-level substance use were identified. The referent class (58.8% of events) was characterized by limited use of any drugs. The Common Drug Use class (12.1%) was characterized by use of alcohol, cannabis, and poppers and the Licit Drug Use class (21.6%) was characterized by use of alcohol alone. The Party 'N' Play (PnP) class (2.3%) was characterized by use of crystal methamphetamine GHB, Poppers, and Erectile Drugs; The Multi-use (3.5%) class was characterized by the PnP substances plus alcohol and ecstasy; and the Cannabis + class was characterized by use of Cannabis, Erectile Drugs, and Ecstasy. Relative to the referent class, all other classes were associated with events with more behavioural and network risk factors for STBBIs-highlighting the need for harm reduction interventions for gbMSM who use these drugs.