Recently formed age-disparate partnerships are associated with elevated HIV incidence among young women in South Africa.
Cross-sectional and cohort studies draw different conclusions on whether age-disparate partnerships increase HIV-acquisition risk for young women. We investigated whether age-disparities were associated with HIV-infection risk early in relationships. This could result in the exclusion of women who seroconverted during high-risk age-disparate partnerships from cohort studies of HIV-incidence – which exclude HIV-positive women – and explain null findings in these studies.
Prospective cohort study
We used data on 15–24 year-old, HIV-negative women in heterosexual partnerships (N=830) in KwaZulu-Natal, South Africa. The association between age-disparate partnering (i.e., male partner ≥5 years older) and subsequent HIV-seroconversion was assessed using Cox hazard models. We examined heterogeneity in HIV-acquisition risk by duration of partnership (defined by quartiles) at cohort enrolment.
During 1139 person-years (mean: 1.4 years) of follow-up, 54 (6.5%) women seroconverted, a weighted HIV-incidence estimate of 4.41/100 person-years (95% CI 3.30–6.06). HIV-acquisition risk did not differ significantly between women in age-disparate vs. age-similar partnerships (aHR 1.10, 95% CI 0.55–2.21). However, for women in the shortest partnership quartile (<1.09 years) at baseline, risk of HIV-seroconversion was higher for women in age-disparate partnerships (aHR 3.13, 95% CI 1.02–9.65, p=0.047). HIV-acquisition was not statistically different by partnership type among women in longer partnerships.
The association between age-disparate partnerships and HIV-acquisition risk is evident early in young women’s relationships. Results provide a potential explanation for null findings in cohort studies, whose research designs may exclude women in such partnerships, and affirms the elevated risk of HIV acquisition for young women in age-disparate relationships.
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