Association of Sexualized Drug Use Patterns with HIV/STI Transmission Risk in an Internet Sample of Men Who Have Sex with Men from Seven European Countries.

We estimated the prevalence of overall sexualized drug use (SDU) and of chemsex in particular, assessed patterns of drug use, and identified subpopulations of men who have sex with men (MSM) where SDU and chemsex are more frequent. Using data from an online survey of 9407 MSM recruited during 2016 in 7 European countries, we calculated the proportion of participants who reported SDU and chemsex (mephedrone, methamphetamine, and/or GHB/GBL) in the last 12 months. We grouped the different drug-use combinations in patterns and described sexual risk behaviors, sexually transmitted infections (STI), and HIV seropositivity for each one of them. Factors associated with SDU and chemsex were assessed with two logistic regression models. SDU was reported by 17.7% and chemsex by 5.2%. Risk indicators increased through the different SDU patterns but were higher within those including chemsex drugs. In the multivariate analysis, chemsex was independently associated with living in Slovenia. Both SDU and chemsex were independently associated with living in Spain; being < 50 years old; living in cities of > 500,000 inhabitants; being open about their sex life; reporting transactional sex; condomless anal intercourse; having received an STI diagnosis and with being HIV positive or having been tested ≤ 12 months ago. Magnitude of associations was higher in the chemsex model. One in five participants reported SDU, but prevalence of chemsex was notably lower. However, the risk profiles and higher prevalence of HIV/STIs among those involved in chemsex suggest the existence of a subpopulation of MSM that could be playing a relevant role in the HIV and STI epidemics, especially in very large cities of some countries.