Background: Age-disparate relationships exacerbate the HIV epidemic in sub-Saharan African adolescent girls and young women (AGYW) aged 15-24 years, whereby significantly older partners may increase their risk of HIV acquisition. To assess associations between partner age and AGYW HIV infection, we used AGYW and cohabitating partner data from Population-based HIV Impact Assessments (PHIAs), nationally-representative household surveys in Zimbabwe, Zambia, Malawi, Eswatini and Lesotho (2015-2017).
Methods: HIV-positive samples were tested for recency (LAg avidity), antiretrovirals (ARVs), and viral load (VL) suppression (HIV RNA< 1000 copies/ml). LAg< 1.5 ODn, VL>1000 copies/ml and no detectable ARVs indicated recent infection. VL>1000 copies/ml denoted viremia, regardless of serostatus. Pooled analyses were done using logistic regression adjusted for AGYW age incorporating survey weights with jackknife estimates of variance for each country. Multivariable analysis assessed determinants between partner age and HIV infection and were further adjusted for country, condom use at last sex, and AGYW past-year sexual partners.
Results: Of 15,982 AGYW tested for HIV, 4,111 (26%) AGYW had partner data, with 2,791 (17%) partners tested for HIV. Median partner age was 27 (Interquartile range [IQR] 24-30) and median age difference was 5 years (IQR 3-8). Viremia was highest in partners aged 35-44 (Table). In the 4,111 AGYW, HIV prevalence was 6.0% (95%CI 5.2-6.9), with almost doubled odds of infection with partners 25-34 (odds ratio [OR]= 1.77, 95%CI 1.12-2.80) and 5 times the odds if partners were 35-44 (OR=4.82, 95%CI 2.84-8.19) or >45 (OR=5.23, 95%CI 2.08-13.42), compared to same age band partners. The odds of recent AGYW infection increased 8% with each additional year of partner age difference (OR=1.08, 95%CI 1.05-1.11). In multivariable analysis, partner serostatus was the strongest predictor of AGYW serostatus (adjusted OR [aOR]=55.19, 95%CI 32.46-93.81, p< 0.001); age was no longer a significant predictor suggesting that the direct effect of male age is as a result of their higher likelihood of HIV infection.
Conclusions: Older cohabitating partners were significantly associated with higher AGYW HIV prevalence and recent infection, likely mediated by their higher HIV prevalence and viremia. Improving ARV coverage and viral suppression in key male age groups may advance AGYW HIV prevention interventions.