Burden of chronic obstructive pulmonary disease attributed to short-term exposure to ambient air pollutants: a time-stratified case-crossover study in Gansu Province, northwestern China

Background Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality and imposes a substantial clinical and medical burden. Short-term exposure to ambient air pollutants can trigger exacerbations and increase healthcare use and costs. However, the avoidable COPD burden attributable to short-term air pollution exposure remains poorly quantified, especially in northwestern China. Comprehensive quantification of this burden is essential to inform targeted air quality and public health policies. Methods This time-stratified case-crossover study analyzed 37,868 COPD-related hospital admissions and 26,473 outpatient visits in Gansu Province during 2019, using data from Gansu Healthcare Security Administration and the ChinaHighAirPollutants dataset. Conditional logistic regression models were used to assess the link between ambient air pollutants and COPD admissions/visits, with measurements of excess fractions, medical fees, and length of stay calculated. Results Short-term exposure to PM 2.5 , NO 2 , CO, and O 3 was associated with increased risks of COPD hospitalization and outpatient visits. In counterfactual modeling analyses assuming pollutant concentrations were reduced to WHO guideline levels, the modeled avoidable COPD burden was 9.19% [95% empirical confidence interval (eCI): 6.45%−11.94%] of hospital admissions, 3,481 (2,442–4,521) admissions, 25,899 (18,168–33,629) in-hospital days, 12.07 (8.46–15.67) million Chinese Yuan (CNY) in hospitalization costs, 8.40% (5.77%−11.03%) of outpatient visits, 2,224 (1,529–2,919) outpatient visits, and 0.25 (0.17–0.33) million CNY in outpatient costs. With WHO air quality guideline levels as the counterfactual reference, PM 2.5 accounted for the largest proportion of the modeled avoidable inpatient COPD burden, whereas O 3 accounted for the largest proportion of the modeled avoidable outpatient COPD burden. Under the theoretical minimum exposure scenario, O 3 was the dominant contributor to outpatient burden, while PM 2.5 and O 3 contributed comparably to inpatient burden. Conclusions Under WHO guideline scenario, PM 2.5 and O 3 mainly contributed to avoidable inpatient and outpatient COPD burden, respectively; under theoretical minimum exposure scenario, PM 2.5 and O 3 contributed comparably to inpatient burden, whereas O 3 was the dominant contributor to outpatient burden.