Malaria burden across 126 tropical countries and territories, 1990–2021: tropical-climate share, sociodemographic correlates, population dynamics, and projections to 2050

Abstract

Malaria remains a major global health challenge, particularly in tropical regions. Although recent global reports describe persistent malaria burden, fewer studies have jointly assessed tropical-climate context, sociodemographic development, demographic decomposition, and future projections across tropical countries. This study aimed to provide an integrated assessment of malaria burden and its ecological correlates among tropical countries and territories. We extracted malaria incidence, prevalence, deaths, disability-adjusted life years (DALYs), years lived with disability (YLDs), years of life lost (YLLs), and corresponding age-standardized rates from the Global Burden of Disease Study 2021 for 126 tropical countries and territories from 1990 to 2021. We assessed spatial patterns, estimated annual percentage changes (EAPCs), age- and sex-specific distributions, ecological correlations with Köppen–Geiger processed-area tropical-climate shares and sociodemographic index (SDI), demographic contributions using Das Gupta decomposition, and autoregressive integrated moving average (ARIMA) projections to 2050. In 2021, malaria burden showed substantial geographic heterogeneity, with the highest age-standardized incidence, mortality, and DALY rates concentrated mainly in West Africa. From 1990 to 2021, most tropical countries experienced declines in age-standardized malaria burden, whereas the absolute number of incident cases increased from 209 to 245 million. Children younger than 5 years had the greatest burden across all indicators, and mortality rates showed a secondary increase among older adults. Decomposition analysis indicated that population growth contributed to increases in absolute malaria numbers, including approximately 103 million additional incident cases, whereas epidemiological improvements and population age-structure changes partially offset this demographic pressure. SDI showed strong negative associations with all age-standardized malaria burden indicators, while processed-area tropical-climate shares showed weak and inconsistent ecological associations. ARIMA projections suggested that age-standardized malaria burden may remain at a high plateau through 2050, with widening prediction intervals over time. Despite substantial progress in malaria control, tropical regions continue to experience persistent malaria burden associated with demographic expansion, socioeconomic disparities, and unequal vulnerability across age groups. Processed-area tropical-climate share alone was not a strong predictor in ecological comparisons, whereas SDI showed robust negative associations with burden. Sustained surveillance, strengthened vector control, health-system investment in low-SDI settings, and targeted interventions for young children and older adults are essential for further reductions.