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Misdiagnosing the relationship between age-disparate partnerships and HIV risk in observational cohort studies: Evidence of heterogeneity in effects by partnership duration at enrolment among young women in South Africa
5th Jun 2019 @ 1:00 pm - 2:00 pm
Cross-sectional and cohort studies draw different conclusions on whether age-disparate partnerships – relationships in which the male partner is 5 or more years older – increase HIV-acquisition risk for young women. Recent longitudinal studies in South Africa found no association between these partnerships and HIV infection, bringing into question the efficacy of HIV-prevention interventions targeting age-disparate partnerships.
We hypothesized that age-disparities are 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. We used prospective cohort data on 15-24 year-old, HIV-negative women in heterosexual partnerships (N=830) in KwaZulu-Natal, South Africa; and assessed the association between age-disparate partnering and subsequent HIV-seroconversion with Cox proportional 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 significantly 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. Our results indicate that 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.
About the Presenter
Dr Brendan Maughan-Brown is an interdisciplinary social scientist with expertise on health services utilisation; behavioural economics; and the social and behavioural determinants of HIV risk. He is a Chief Research Officer at the Southern Africa Labour and Development Research Unit, University of Cape Town.
His current research focuses on understanding the psychosocial and structural barriers to antiretroviral therapy for HIV, and testing interventions to increase treatment uptake. He is also conducting research on a novel intervention to improve handwashing and health among young children; and research to advance understanding of the factors contributing to high HIV incidence rates among young women in South Africa.