Age differences in sexual partners and risk of HIV-1 infection in rural Uganda

Objectives: To assess whether differences in age between sexual partners affect the risk of HIV infection in female adolescents and young adults. Methods: A total of 6177 ever sexually active women aged 15 to 29 years completed a sociodemographic and sexual behavior questionnaire and provided a blood sample for HIV-1 serology. The age difference between partners was categorized as men 0 to 4 years older (referent group), 5 to 9 years older and 10 or more years older. HIV prevalence and incidence were assessed, and adjusted RR was estimated by multivariate regression. Results: Prevalent HIV-1 infection in female participants increased with older male sexual partners. Among women aged 15 to 19 years, the adjusted risk of HIV infection doubled (RR = 2.04; 95% CI: 1.29-3.22) among those reporting male partners 10 or more years older compared with those with male partners 0 to 4 years older; among women 20 to 24 years of age, the RR was 1.24 (95% CI: 0.96-1.60). The attributable fraction (exposed) of prevalent HIV infection in women aged 15 to 24 years associated with partners 10 or more years older was 9.7% (95% CI: 5.2-14.0). HIV incidence did not increase with differences in age of partners. Conclusion: The age difference between young women and their male partners is a significant HIV risk factor, suggesting that high HIV prevalence in younger women is caused, in part, by transmission from older male partners.