RESUMO
BACKGROUND: Structural interventions are endorsed to enhance biomedical and behavioural HIV prevention programmes for adolescents. Aiming to inform future interventions, we evaluated longitudinal associations between six structural factors and five HIV risk practices in a cohort of adolescents in South Africa. METHODS: We used three rounds of data between 2014-2018 on 1046 adolescents living with HIV and 483 age-matched community peers in South Africa's Eastern Cape (Observations = 4402). We used multivariable random effects within-between logistic regression to estimate sex-specific associations between six time-varying structural factors - number of social grants, education enrolment, days with enough food, caregiver supervision, positive caregiving, and adolescent-caregiver communication - and five HIV risk practices - multiple sexual partners, transactional sex, age-disparate sex, condomless sex, and sex on substances. We calculated probability differences, contrasting predicted probabilities at average and maximum values of structural factors associated with multiple risk practices. FINDINGS: The sample mean age was 15.29 (SD: 3.23) years and 58% were female. In females, compared to average, maximum positive caregiving scores were associated with lower probability of transactional sex (-1.06 percentage points [ppts], 95%CI=-1.60; -0.52ppts), and age-disparate sex (-0.73ppts; 95%CI=-1.26; -0.19ppts); maximum caregiver supervision scores were associated with lower probability of multiple sexual partners (-3.11ppts; 95%CI=-3.87; -2.35ppts) transactional sex (-1.07ppts, 95%CI=-1.42; -0.71ppts), age-disparate sex (-0.67ppts; 95%CI=-1.08; -0.25ppts), condomless sex (-3.96ppts; 95%CI=-5.65; -2.26ppts), and sex on substances (-0.93ppts; 95%CI=-1.50; -0.37ppts); and, seven days with enough food was associated with lower probability of multiple sexual partners (-1.18ppts, 95%CI=-2.06; -0.30ppts), and transactional sex (-0.91ppts; 95%CI=-1.41; -0.42ppts). Relative to non-enrolment, education enrolment was associated with lower probability of age-disparate sex (-3.18ppts; 95%CI=-5.35; -1.01ppts), and condomless sex (-11.32ppts; 95%CI=-19.15; -3.49ppts). In males, compared to average, maximum caregiver supervision scores were associated with lower probability of multiple sexual partners (-2.83ppts; 95%CI=-3.66; -2.00ppts), transactional sex (-0.90ppts; 95%CI=-1.20; -0.60ppts), age-disparate sex (-0.46ppts; 95%CI=-0.77; -0.15ppts), and sex on substances (-1.42ppts; 95%CI=-2.06; -0.78ppts). No other structural factors were associated with multiple risk practices. INTERPRETATION: Structural interventions to improve food security and education enrolment among adolescent girls, and positive and supervisory caregiving among adolescent girls and boys are likely to translate into crucial reductions in HIV risk.