Identification and characterization of latent classes based on drug use among men who have sex with men at risk of sexually transmitted infections in Amsterdam, the Netherlands.

Abstract

Men who have sex with men (MSM) are at high risk for both drug use and sexually transmitted infections (STI). We aimed to (1) identify subgroups of drug use during sex among MSM in Amsterdam and after classifying participants and (2) compare sexual behaviour and STI across groups. Cross-sectional study. Latent class analysis was used to identify subgroups with similar drug use patterns, between which sexual behaviour and STI prevalence were compared. Four different studies conducted at the STI out-patient clinic in Amsterdam, the Netherlands, between January 2014 and June 2016. A total of 1130 self-declared MSM, aged ≥18years. Self-reported drug use, laboratory-confirmed STI, socio-demographics, sexual behaviour (including number of partners), condom use. Median age was 40years [interquartile range (IQR)=32-47]. We identified five latent classes of users, which we labelled: 'no substance' (n=162), 'alcohol' (n=159), 'nitrites and erectile dysfunction drugs (EDD)' (n=286), 'polydrug' (n=257) and 'chems' (n=266). Median number of sex partners significantly differed across classes (P<0.001), ranging from two (IQR=1-6) in the 'no substance' class to 20 (IQR=10-45) in the 'chems' class. The proportion of MSM reporting condomless anal sex also differed across classes (P<0.001), ranging from 45.6% in the 'no substance' class to 86.5% in the 'chems' class. Compared with the 'no substance' class, the odds of STI were 3.9-fold [95% confidence interval (CI)=1.1-14.4] higher in the 'alcohol' class, 8.9-fold (95% CI=2.7-29.2) higher in the 'nitrites and EDD' class, 12.8-fold (95% CI=3.9-41.9) higher in the 'polydrug' class and 15.0-fold (95% CI=4.6-48.8) higher in the 'chems' class. There are five distinct classes of drug use in a sexual context among men who have sex with men in Amsterdam, the Netherlands. Classes with higher levels of drug use appear to coincide with higher levels of sexual risk behaviour and sexually transmitted infections.