Chemsex, sexually transmitted infections, and pre-exposure prophylaxis among men who have sex with men: longitudinal analyses of sexual health clinic attendees in Montréal
Bibliographic record
Abstract
Background: Chemsex –the use of illicit substances during sex to enhance pleasure– has become more prevalent in the last decade among gay, bisexual and other men who have sex with men (gbMSM). This has raised public health concerns because chemsex can be associated with transmission of HIV and other sexually transmitted infections (STIs). Pre-exposure prophylaxis (PrEP) is highly effective at preventing HIV and is recommended for gbMSM and transgender women at elevated risk of HIV acquisition. As PrEP can provide an important prevention tool for people who practice chemsex, it is important to better understand the role of chemsex in PrEP use and STI incidence.Objectives: Understand the evolving patterns of chemsex practices among gbMSM and transgender women consulting for PrEP in Montréal (Canada) and their impact on STI transmission among PrEP users by: (1) describing temporal trends in chemsex practices and their impact on PrEP trajectories, and (2) estimating the impact of chemsex on incidence of gonorrhea and chlamydia among PrEP users.Methods: The l’Actuel PrEP Cohort was established in 2013 at the Clinique médicale l’Actuel, a major sexual health clinic in Montréal. For the purposes of this thesis, the cohort was restricted to adult (≥18 years-old) gbMSM and transgender women who consulted for PrEP between 2013–2020. This dataset includes baseline sociodemographic and behavioural data, and quarterly follow-up behavioural and STI screening data. I first described the sociodemographic profile of clients who consulted for PrEP, characterized chemsex and polysubstance use trends over time, and evaluated PrEP trajectories. Then, for the second objective, I used survival analyses to estimate the effect of chemsex at baseline on incidence of gonorrhea and chlamydia, focusing on the 24 months following PrEP initiation. I also investigated the role of polysubstance use and potential effect modification by age, education, and income.Results: A total of 2,923 clients consulted for PrEP between 2013–2020 (2,910 cisgender gbMSM, 6 transgender gbMSM, 7 transgender women). Among these clients, 24% reported any chemsex and 13% reported polysubstance use in the past year. Ecstasy (14%), GHB (13%), and cocaine (12%) were the most commonly reported chemsex substances. Prevalence of chemsex and polysubstance use decreased over time. The proportion of clients initiating PrEP (73%) was similar between groups, and the median time to discontinuation was also similar: 6.5 months (95% CI: 5.3–7.2) in the chemsex group compared to 6.9 months (95% CI: 6.3–7.5) in the no-chemsex group. There were 2,086 clients (2,079 cisgender gbMSM, 3 transgender gbMSM, 4 transgender women) who initiated PrEP, contributing 1,477 person-years of follow-up. There was no incident HIV infection among clients on PrEP. When controlling for age, education, income, PrEP regimen, and year of baseline consultation, chemsex was linked to a 32% higher hazard of gonorrhea or chlamydia diagnosis (adjusted HR=1.32; 95% CI: 1.10–1.57). This effect was stronger among clients reporting polysubstance use (adjusted HR=1.51; 95% CI: 1.21–1.89). The strength of the effect of chemsex on STI incidence varied by age, education, and income.Conclusions: One in four gbMSM consulting for PrEP at a large Canadian sexual health clinic reported chemsex in the past year. Chemsex, however, is not an obstacle to PrEP initiation or persistence. Among PrEP users, chemsex at baseline is linked to increased incidence of gonorrhea and chlamydia. Incidence was higher for people who report two or more chemsex substances. The high prevalence of chemsex practices and high STI incidence highlight the need for integrated services addressing unmet needs at the intersection of sexual health and substance use. The high STI incidence also stresses the importance of PrEP as an effective HIV prevention tool for this population
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.002 |
| Bibliometrics | 0.002 | 0.005 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.003 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".