Global, regional, and national age-gender-specific trends, decomposition analysis, and Bayesian age-period-cohort modelling for projections of the burden of leishmaniasis: A population-based ecological study.

Leishmaniasis, a neglected tropical disease transmitted by sandflies, continues to pose a significant public health challenge, especially in tropical and subtropical regions. This study aims to deliver a comprehensive analysis of the global burden of leishmaniasis, exploring trends, disparities, and future projections to inform and enhance public health strategies. Using the data from the Global Burden of Disease database, we analysed leishmaniasis prevalence, incidence, mortality, and disability-adjusted life years (DALYs) across 204 countries and territories from 1990 to 2021. We calculated age-standardised rates (ASRs) and estimated annual percentage changes (EAPCs) to assess trends. The Kitagawa decomposition method was employed to quantify contributions of population ageing, population growth, and epidemiological changes. A Bayesian age-period-cohort (BAPC) model was used to project disease burden through 2036. Globally, the age-standardised prevalence rate (ASPR) showed a slight increase from 1990 to 2021 (EAPC = 0.71%, 95% CI: 0.66-0.76%), while the age-standardised incidence rate (ASIR), mortality rate (ASMR), and DALY rate (ASDR) declined (ASIR EAPC = -0.51%, 95% CI: -1.09-0.05%; ASMR EAPC = -6.84%, 95% CI: -7.74 to -5.93%; ASDR EAPC = -5.17%, 95% CI: -5.99 to -4.33%). In 2021, there were 6.21 × 106 (95% UI: 5.83 × 105-6.69 × 106) prevalent cases and 5.48 × 103 (95% UI: 1.61 × 103-1.78 × 104) deaths globally. Marked disparities were observed across Socio-demographic Index (SDI) regions, with low SDI regions bearing the highest burden (ASPR = 139.66 per 100,000). The Syrian Arab Republic had the highest ASPR (4.73 × 103 per 100,000), while Romania and Serbia had the lowest (0.01 per 100,000). Decomposition analysis revealed that population growth was the primary driver of increased prevalence burden globally (78.5%), while epidemiological changes contributed to reduced incidence (-288%) and mortality (-118.66%) burdens. Projections indicate that by 2036, male ASPR will rise to 119.31 (95% UI: 92.32-146.30) per 100,000, while ASIR and ASMR will remain stable. Despite declining incidence and mortality, leishmaniasis prevalence is projected to increase, with persistent significant disparities across regions, ages, and genders. Targeted interventions addressing population growth, epidemiological factors, and socio-economic determinants are crucial for reducing the future burden of leishmaniasis, particularly in low SDI regions.