55 The Epidemiology of Substance Use and Sexual Risk Behavior among Men Who Have Sex with Men: Implications for HIV Prevention Interventions Grant Colfax San Francisco Dept of Publ Hlth, CA, USA

Substance use is highly prevalent among men who have sex with men (MSM), and plays an integral part in fueling the continuing HIV epidemic in this population.  This presentation will review the epidemiology of substance use and associated sexual risks, the relationship between substance use and HIV seroconversion in the context of other risk factors, and potential approaches to HIV prevention interventions for MSM substance users.

Substances commonly used by MSM include alcohol, methamphetamines, amyl nitrites (poppers), and club drugs such as ecstasy and gamma hydroxybutyrate (GHB). While general associations between substance use and sexual risk behavior have been documented since the late 1980’s, the causal relationships between substance use and sexual risk have until recently remained unclear, with most prior analyses potentially confounded by a variety of contextual effects including personality disposition, partner type, and relationships status.  More recent analyses have demonstrated a strong correlation between substance use and sexual risk after controlling for these potential confounders.  Emerging data demonstrate that the relationship between substance use and sexual risk is complex and depends on the specific types of substances used, dosing, contextual factors, and frequency of use.  In general, studies have shown that methamphetamine, amyl nitrite, cocaine, and heavy alcohol use are independently associated with sexual risk, and, in some cases, independently associated with HIV seroconversion, even after controlling for behaviors such as unprotected sex and numbers of sexual partners.  In contrast, there is less evidence that ecstasy, GHB, or light alcohol use correlates with sexual risk.

The correlations between use of specific substances and HIV risk behavior make it clear that interventions to reduce methamphetamine, amyl nitrite, cocaine, and heavy alcohol use among MSM should be tested to determine if reductions in use of these substances are associated with corresponding reductions in sexual risk. Given the different psychological and physical effects of these substances, it is likely that a variety of interventions will need to be developed. To date, few substance-use interventions for MSM have been rigorously tested or have demonstrated sustained reductions in sexual risk behaviors, although several approaches show promise, including pharmacologic, contingency management, and risk-reduction counseling interventions.