Pre-exposure prophylaxis and bacterial sexually transmitted infections (STIs) among gay and bisexual men
Trevor A Hart1,2, Syed W Noor3,4, Graham W Berlin3
1Department of Psychology, Ryerson University, Toronto, Ontario, Canada trevor.hart@ryerson.ca.
Objectives:
While pre-exposure prophylaxis (PrEP) prevents HIV acquisition among gay, bisexual and other men who have sex with men (GBM), PrEP-using GBM may be more likely to engage in sexual behaviours associated with bacterial STIs. We examined associations between PrEP use, condomless anal sex (CAS), number of anal sex partners, oral sex and bacterial STI diagnoses among GBM living in Canada's three largest cities.
Methods:
Among HIV-negative/unknown-status GBM in the baseline of the Engage cohort study, we fit a structural equation model of the associations between any PrEP use, sexual behaviours and bacterial STI diagnosis. We estimated direct and indirect paths between PrEP use and STI via CAS, number of anal sex partners and oral sex.
Results:
The sample included 2007 HIV-negative/unknown status GBM in Montreal, Toronto and Vancouver. There was a significant direct association between PrEP use and current STI diagnosis (β=0.181; 95% CI: 0.112 to 0.247; p<0.001), CAS (β=0.275; 95% CI: 0.189 to 0.361; p<0.001) and number of anal sex partners (β=0.193; 95% CI: 0.161 to 0.225; p<0.001). In the mediated model, the direct association between PrEP use and STIs was non-significant. However, the indirect paths from PrEP to CAS to STIs (β=0.064; 95% CI: 0.025 to 0.120; p=0.008), and from PrEP to greater number of anal sex partners to CAS to STIs were significant (β=0.059; 95% CI: 0.024 to 0.108; p=0.007).
Conclusions:
Our study adds to the growing awareness that PrEP use among GBM may be associated with bacterial STIs because PrEP users have more anal sex partners and are more likely to engage in CAS. The results underscore the importance of providing effective STI counselling and regular testing to PrEP users, adapting PrEP care and related STI testing to individual needs, and the need for effective prevention strategies for bacterial STIs.
Insights
Pre-exposure prophylaxis (PrEP) use among gay, bisexual, and other men who have sex with men (GBM) is linked to increased bacterial STI diagnoses, primarily through condomless anal sex and a higher number of anal sex partners.
Area of Science:
- Public Health
- Infectious Diseases
- Sexual Health
Background:
- Pre-exposure prophylaxis (PrEP) is effective in preventing HIV acquisition among men who have sex with men (MSM).
- However, PrEP use may be associated with changes in sexual behaviors that increase the risk of bacterial sexually transmitted infections (STIs).
Purpose of the Study:
- To examine the associations between PrEP use, sexual behaviors (condomless anal sex, number of anal sex partners, oral sex), and bacterial STI diagnoses among gay, bisexual, and other men who have sex with men (GBM) in Canada.
Main Methods:
- A structural equation model was used to analyze data from the Engage cohort study, including 2007 HIV-negative/unknown status GBM in Montreal, Toronto, and Vancouver.
- The model assessed direct and indirect paths between PrEP use and bacterial STI diagnosis, mediated by condomless anal sex (CAS) and the number of anal sex partners.
Main Results:
- A significant direct association was found between PrEP use and current STI diagnosis, CAS, and number of anal sex partners.
- The direct association between PrEP use and STIs became non-significant in the mediated model.
- Significant indirect paths were identified from PrEP use to CAS to STIs, and from PrEP use to a greater number of anal sex partners to CAS to STIs.
Conclusions:
- PrEP use among GBM is associated with bacterial STIs, mediated by increased condomless anal sex and a higher number of anal sex partners.
- These findings highlight the critical need for enhanced STI counseling, regular testing, and tailored prevention strategies for PrEP users.
- Adapting PrEP care and STI testing to individual needs is essential for mitigating bacterial STI risks in this population.
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