Do People Really Know Their Sex Partners?

BACKGROUND AND OBJECTIVE: An individual's risk of sexually transmitted infections (STIs) has been associated empirically with the individual having concurrent sexual partners (individual's concurrency) and, theoretically, with the individual's partner having concurrent partners (partner's concurrency). GOALS: The goals of this study were to assess the relationship of STI to individual's concurrency, the partner's concurrency, and awareness of the partner's concurrency. STUDY DESIGN: We recruited 192 individuals aged 18 to 30 from sexually transmitted disease and family planning clinics in 96 partner dyads that reported first sexual contact during the previous 3 months. All individuals underwent computer interviews and testing for Chlamydia trachomatis, Neisseria gonorrhoeae, and Trichomonas vaginalis. Individuals' self-reports of concurrency and perceptions of partners' concurrency were compared within dyads by kappa statistic; associations of STI with individual's concurrency, partner's concurrency, and knowledge of partner's concurrency were examined using chi-squared analysis, t tests, and multivariate logistic regression. RESULTS: Only 26% of individuals whose partners had other partners were aware of this (kappa = 0.17 for agreement of perceptions vs. partners' reports of concurrency). In multivariate models, STI in individuals was independently associated with partners' concurrency (odds ratio OR, 3.6), lack of awareness of partner's concurrency (OR, 4.5), perceiving a partner to have concurrent partners when the partner did not (OR, 4.7), living in south San Diego, and sexual contact within 1 week of acquaintance, but not with individuals' concurrency. CONCLUSION: This study demonstrates that STI is associated with partner's concurrency and with not knowing one's partner's behavior.