Substance use in sexual context among Spanish resident men who have sex with men.

We analysed patterns of sexualized drug use (SDU) and pinpointed the one with the highest risk for the acquisition/transmission of HIV/Sexually Transmitted Infections (STIs) in a sample of men who have sex with men (MSM) residing in Spain. Additionally, we also identified the most affected subpopulations by highest risk SDU pattern. In 2016, we promoted an online survey in gay dating apps. We estimated the prevalence of several HIV/STI risk indicators for each identified SDU pattern. We built two different Poisson regression models identifying factors associated to the pattern associated with the highest risk. All analyses were carried out by HIV status. Of 2,883 MSM, 21.9% self-reported SDU in the last 12 months. All patterns of SDU were more frequent in HIV+ MSM. Of the four SDU patterns identified (chemsex, recreational drugs, sexual performance enhancing drugs, and cannabinoids), the most frequent was chemsex (21.9% in HIV+ vs 6.6% in HIV-). It also comprised the highest risk profile for HIV/STI. Among HIV-, chemsex was associated with living in a city of > 1,000,000 inhabitants, living sexuality in an open way and having been paid for sex, having had unprotected anal intercourse (UAI) in the last 12 months and having ever received an STI diagnosis. Among HIV+, it was associated with being 30-49 years old, having paid for sex, having had UAI and having been diagnosed with an STI in the last 12 months. Given its high prevalence, especially among HIV positive individuals, and its association with subpopulations with high-risk behaviour, chemsex could be playing a relevant role in the acquisition/transmission of HIV and other STIs.