Regional heterogeneity in the association between antiretroviral therapy coverage and HIV epidemiology in Sub-Saharan Africa: a longitudinal ecological study of 38 countries (2010–2022)

Abstract Introduction : Antiretroviral therapy (ART) coverage has expanded rapidly in sub-Saharan Africa, but the population-level impact on HIV incidence, mortality and prevalence across different sub-regions remains uncertain. We quantified the association between ART coverage and these epidemiological indicators from 2010 to 2022. Methods : We conducted a longitudinal ecological study using country-level data from 38 sub-Saharan African countries (494 observations) from UNAIDS, the World Bank and the UNDP. Fixed-effects panel regression models with log-transformed variables estimated elasticities: β represents the percentage change in the outcome per 1% change in ART coverage. Results are presented per 10% ART increase for interpretability. Regional interaction terms (East Africa as reference) tested effect heterogeneity, with real effects in other regions calculated as β_ART + β_interaction. Bootstrapping generated 95% confidence intervals (CIs) for overall percentage changes. Results : Regional ART coverage increased from 22% to 75% between 2010 and 2022. Overall, HIV incidence fell by 65% (95% CI 60–70), mortality by 72% (68–76), and prevalence by 33% (30–36). Regarding incidence, a 10% increase in ART coverage was associated with a 1.6% reduction in East Africa (β_ART = − 0.16, 95% CI − 0.24 to − 0.08); the effect was significantly attenuated in West Africa (real β = − 0.02, 0.2% reduction; interaction p = 0.003) but similar in Central and Southern Africa (interaction p > 0.05). For mortality, a 10% ART increase was associated with a 4.2% reduction in East Africa (β_ART = − 0.42, 95% CI − 0.49 to − 0.35); significant attenuation was observed elsewhere, with real effects of − 0.26 (2.6% reduction) in West Africa, − 0.21 (2.1%) in Southern Africa, and − 0.32 (3.2%) in Central Africa (all interaction p < 0.05). For prevalence, a 10% ART increase was associated with a 1.0% reduction in East Africa (β_ART = − 0.10, 95% CI − 0.13 to − 0.07); the effect was similar in West Africa (interaction p = 0.60) but significantly attenuated in Central and Southern Africa (real β = − 0.04, 0.4% reduction; interaction p < 0.01), and the association was strongly modified by the incidence–mortality ratio (interaction β = 0.29, p < 0.001). Had ART coverage remained at 2010 levels, an estimated 1.2 million (95% CI 1.0–1.4) additional deaths would have occurred. Conclusion : ART scale-up substantially reduced HIV incidence and mortality across all sub-Saharan African regions, with significant though attenuated effects in West, Southern and Central Africa. Prevalence is an unreliable standalone indicator of ART programme success. Regional tailoring of ART strategies and continued health system investments remain essential.