Substance use and HIV-risk behaviors among HIV-positive men who have sex with men in China: repeated measures in a cohort study design.

Global literature revealed that seropositive men who have sex with men (MSM) posed an even higher risk compared to their seronegative counterparts. Identifying risk factors that contribute to HIV-risk behaviors will help to curb the rapid HIV transmission among this group. Our hypothesis was that MSM with substance use were more likely to conduct HIV-risk behaviors, even after accounting for repeated measures. In the current study, we employed a cohort study design by following a group of 367 HIV-positive MSM up to four visits for one year to collect information regarding their sexual behaviors and history of substance use in the past three months. We used Generalized Estimating Equations (GEE) models to account both within- and between-subject variation when assessing associations between substance use and HIV-risk behaviors. A total of 367 MSM were included at the baseline with a mean age of 29.6 years. After accounting for potential confounders and time-varying effects, our models indicated that drug and alcohol use increase HIV risks at the population level by increasing risks of drinking alcohol before sex, having unprotected sex with men and seropositive partners, having more lifetime female sex partners and having a higher number of male sexual partners in the past three months. The current study is one of the first studies with repeated measures to evaluate the association between substance use and sexual risk behaviors among MSM in China. Findings in the current study have several implications for future research. We call for more rigorous study design for future research to better capture changes of risky behaviors among this at-risk population.