Burden of non-COVID-19 lower respiratory infections and etiologies in China and globally: An analysis for the global burden of disease study 2021.

Background: Non-COVID-19 lower respiratory infections (LRIs) represent a persistent public health concern in China and globally. However, comprehensive assessments of their long-term spatiotemporal trends remain limited. This study aimed to quantify the burden of LRIs by age, sex, and geographic region across China and globally from 1990 to 2021. Methods: Using standardized methodologies from the Global Burden of Disease Study 2021, we estimated LRI incidence and mortality globally and across 33 provincial-level units in China by sex, age, and year. Attributable incidence and mortality were further analyzed by underlying etiologies and risk factors, with corresponding 95 % uncertainty intervals. Results: In 2021, LRI accounted for 343.6 (95% UI: 325.2-363.5) million episodes and 2.2 (95% UI: 2.0-2.4) million deaths worldwide, corresponding to age-standardized incidence and mortality rates of 4283.6 (95% UI: 4057.0-4524.9) episodes per 100,000 population and 28.7 (95% UI: 25.9-31.1) per 100,000 population, respectively. This reflected a decline of 32.8 % and 53.6 % since 1990. China contributed 44.7 (95% UI: 41.8-47.8) million episodes and 206,930.2 (95% UI: 171,260.9-251,990.5) deaths in 2021, with respective age-standardized rates of 2853.8 (95% UI: 2664.0-3067.6) episodes per 100,000 population and 14.0 (95% UI: 11.7-17.0) per 100,000 population. Between 1990 and 2021, the age-standardized incidence and mortality rates in China declined by 47.9 % and 76.9 % which were higher than the global average. This progress was primarily driven by reductions in children under 5 years. Older individuals ≥70 years exhibited the highest burden. In 2021, Guangdong reported the highest age-standardized incidence, while Guizhou had the highest mortality. Streptococcus pneumoniae was the leading cause of LRI-related deaths. Ambient particulate matter pollution, smoking, and low temperature were the primary risk factors, with notable sex-specific differences. Conclusions: Despite marked improvements, LRIs remain a major contributor to morbidity and mortality in China, particularly among children and older adults. Addressing the residual burden will require targeted strategies, including enhanced diagnostics, expanded vaccination, air quality control, and strengthened healthcare in high-burden provinces.