Background: The prevalence of and the risk for sexually transmissible infections (STIs) for women engaging in same-sex sexual behaviour was investigated among women attending an STI clinic.
Methods: Data from electronic medical records were reviewed and logistic regression used to estimate the odds ratio (OR) of STIs. Women reporting life-time exclusively female partners (WSW) and women reporting female and male partners (WSWM) were compared with women reporting exclusively male partners (WSM). Outcomes included: Chlamydia trachomatis, Mycoplasma genitalium, Neisseria gonorrhoea, HIV and syphilis.
Results: The study population comprised 103564 women (WSW 641, WSWM 12010 and WSM 90913). Overall prevalence of STIs was 8%. Crude OR of STIs for WSW: 0.56 (95% CI 0.39-0.81), for WSWM: 0.99 (95% CI 0.92-1.06) compared with WSM. Multivariate analysis revealed an interaction effect between same-sex sexual behaviour and smoking. Among non-smokers; WSW adjusted OR was 0.41 (95% CI 0.21-0.80), WSWM adjusted OR was 0.91 (95% CI 0.81-1.02) compared with WSM. Among smokers; WSW adjusted OR was 1.03 (95% CI 0.63-1.67) for WSWM adjusted OR was 1.00 (CI 95% 0.93-1.13), compared with WSM.
Conclusion: This study, including the largest cohort of women reporting life-time exclusively female partners in an STI study, shows that WSW generally are at lower risk for acquiring STIs than WSM. Smoking WSW, however, had the same risk for acquiring bacterial STIs as WSM and WSWM. Our study suggests that all WSW should receive the same encouragement to test for STIs as WSM.