June 7, 2006
In the current study, researchers investigated the association of methamphetamine, sildenafil, and other substance use with unprotected receptive and insertive anal sex among men who have sex with men (MSM) through an encounter-specific analysis. With data from a cross-sectional, community-based survey of MSM in San Francisco regarding behavior during their most recent anal sex encounter, researchers used multivariate regression to analyze independent associations of specific substance use and demographic variables with unprotected anal sex behaviors.
The sample (n=388) was diverse in terms of race/ethnicity, age, income, education, HIV status, and homosexual/bisexual identification. Of the sample, 53 percent reported unprotected anal sex, including insertive (29 percent) and receptive (37 percent) during their most recent anal sex encounter. Twelve percent reported unprotected insertive anal sex with an HIV discordant partner or partner of unknown serostatus; 17 percent reported unprotected receptive anal sex with an HIV discordant partner or partner of unknown serostatus. Fifteen percent of the sample used methamphetamine before or during the encounter; 6 percent used sildenafil; and 2 percent used both drugs.
In multivariate analysis controlling for demographic factors and other substance use, the investigators found methamphetamine use was associated with unprotected receptive (odds ratio (OR), 2.03; 95 percent confidence interval (CI), 1.09 to 3.76) and sildenafil use was associated with unprotected insertive (OR, 6.51; CI, 2.46 to 17.24) anal sex. Effects were stronger with HIV discordant or unknown sex partners specifically.
"Encounter-specific associations of methamphetamine and sildenafil use with unprotected receptive and insertive anal sex, respectively, indicate the importance of assessment specificity and tailoring risk reduction efforts to address certain drugs and sexual behavioral roles among MSM," the authors concluded.