Delineation of chemsex patterns of men who have sex with men in association with their sexual networks and linkage to HIV prevention

Background: Previous studies have shown that men who have sex with men (MSM) and who engage in drug use in sexualized contexts (chemsex) were more likely to be HIV positive. Their social networks and adoption of HIV prevention measures have, however, not been fully investigated. We aim to compare the sexual behavior, HIV prevention efforts and social networks of MSM by the intensity and patterns of their drug use. Methods: Data from respondents of a community-based, cross-sectional survey (PRiSM) conducted among MSM in Hong Kong in 2017 were collected retrospectively. Characteristics of MSM engaged and not engaged in chemsex were compared in logistic regressions, delineated by latent class analysis (LCA) and compared in multinominal logistic regression. Findings: Of 4133 respondents, 3044 were sexually active with an HIV prevalence of 6.5%. The prevalence of chemsex engagement in the preceding 6 months was 12%, after excluding use of poppers or erectile dysfunction agents (EDA) alone. Four types of drug user were identified by LCA: Minimal (mainly poppers), low-threshold (mainly poppers and EDA), medium-threshold (mainly methamphetamine, GHB, poppers and EDA) and intense (extensive use of different types of drug). Medium-threshold and intense drug users were more likely to be HIV positive, be diagnosed with sexually transmitted infections, make gay friends through mobile apps and sex parties, and intend to take pre-exposure prophylaxis (PrEP). Medium-threshold drug users had a more influential role in their social network, as shown by their higher centrality in mobile apps network. Conclusion: Chemsex engagement in MSM is significantly associated with HIV infection in Hong Kong. The HIV transmission risk could however be offset by the inclination of MSM belonging to medium-threshold and intense drug users to take PrEP, should the intervention become accessible to the community. Further mobile apps could be a good channel to access MSM who are medium-threshold drug users.