Background Cross-sectional studies have shown an independent association between receptive anal sex and active syphilis among men who have sex with men (MSM) and transgender women (TW). This study sought to evaluate the relationship between role in anal sex and incident syphilis in a cohort of MSM/TW in Lima, Peru.
Methods We are conducting an observational cohort study of MSM/TW recruited from two STI clinics. In quarterly follow-up visits, participants provide behavioural data, and serologic testing is performed for HIV and syphilis. Participants’ roles in anal sex reported at baseline were categorised as insertive, receptive or versatile. Participants with active syphilis (i.e. RPR titer ≥1/16 and TPPA ≥1:80) were treated according to CDC guidelines. We evaluated the relationship between anal sex role and incident syphilis with a multivariate logistic regression model using generalised estimating equations for longitudinal data.
Results At baseline, among the 401 participants, mean age was 31.6 years (SD 9.6); when asked about their role in anal sex, 32%, 46% and 22% reported being receptive, versatile and insertive, respectively. Prevalence of active syphilis was 22% at baseline; incidence was 18% and 23% at the third and sixth follow-up visits, respectively. In multivariate analysis, after controlling for age, education, employment, income, gender identity, number of sexual partners, alcohol/drug use, unprotected sex, and HIV, the odds for incident syphilis were higher among people who had defined their anal sex role as receptive (aOR = 2.48 (95% CI 1.23–5.02)) or versatile (aOR = 2.38 (95% CI 1.27–4.47)) as compared to the insertive role.
Conclusions MSM/TW who defined their role in anal sex as receptive or versatile showed a significantly higher syphilis incidence in this longitudinal analysis. Further research is needed to assess whether this association can be explained by behavioural/sexual networking patterns, the existence of a biological substrate, or both.
Disclosure of interest statement All authors declare no conflicts of interest.