Global, regional, and national trends in the disease burden and inequality of lower respiratory infections, 1990 to 2021: A systematic analysis of the 2021 global burden of disease study

This study analyzed the disease burden of lower respiratory infections (LRIs) and associated health inequalities globally, regionally, and nationally from 1990 to 2021, aiming to provide evidence-based insights for optimizing public health policies. Leveraging data from the 2021 global burden of diseases (BODs), injuries, and risk factors study (global burden of diseases (GBD) 2021), we comprehensively analyzed the disease burden and health inequality levels. Using frontier analysis, we aimed to elucidate the impact of national and regional development. Decomposition analysis was employed to dissect the contributions of epidemiological changes, aging, and population growth, while age-period-cohort (APC) modeling was adopted to explore temporal trends. Compared to 1990, the global burden of LRIs in 2021 exhibited a downward trend; however, significant disparities persisted across socio-demographic index (SDI) strata. In 2021, low-SDI regions recorded the highest age-standardized disability-adjusted life year (DALY) rates, with the most pronounced disease burden observed in sub-Saharan Africa. After adjusting for population size, the top 5 countries with the highest absolute disease burden were India, Nigeria, China, Pakistan, and Ethiopia, collectively accounting for 45.1% of the global burden. From 1990 to 2021, health inequalities narrowed with increasing SDI. Among all regions, China exhibited the most significant improvement, whereas the 15 countries with the largest improvement gaps were predominantly concentrated in low- and low-middle-SDI regions. Globally, reductions were primarily driven by epidemiological transitions. However, in Asia and sub-Saharan Africa, population growth substantially offset these gains. Children under 5 and adults over 65 represented the highest-burden groups. Globally, pre-2005 improvements were predominantly driven by high-SDI regions; however, post-2005, while global trends stabilized, middle-high-SDI regions exhibited a significant decline. Prior to 1947, changes were largely influenced by high-SDI regions. In contrast, over the past 3 decades (since 1987), the most significant improvements were observed in middle-high-SDI and middle-SDI regions, reflecting substantial advancements in these populations. Health inequalities related to LRIs are significantly influenced by geographic and national factors. Although epidemiological improvements have improved LRI-related health outcomes globally, these gains are offset by challenges such as population aging and growth. Targeted interventions are urgently needed to address the underlying drivers of health inequality.