Associations Between Air Pollution and Hospitalization of Patients with Chronic Obstructive Pulmonary Disease in Kashi, China: A Time-Stratified Case-Crossover Study.

Objective: To investigate associations between air pollutants and hospitalization of patients with chronic obstructive pulmonary disease (COPD) in Kashi, and to identify susceptible populations.

Methods: We conducted a retrospective study of COPD patients in Kashi between 2012 and 2022. Daily pollutant concentrations were matched to residential addresses for individual exposure assessment. A time-stratified case-crossover design with conditional logistic regression was used to evaluate associations between pollutants and COPD hospitalization. Stratified analyses were performed by age, gender, smoking history and hospitalization season. Sensitivity analysis was conducted by excluding hospitalizations during the COVID-19 pandemic to test result robustness.

Results: A total of 68,482 patients were included. The strongest significant association between particulate matter (PM₁₀) and COPD hospitalization was identified at lag day 4, particulate matter (PM_2.5), PM₁₀, nitrogen dioxide (NO2) and carbon monoxide (CO) exposures generally had relationships of COPD hospitalization [OR (95% CI): 1.015 (1.002-1.032), 1.008 (1.002-1.016), 1.034 (1.008-1.067), and 1.034 (1.005-1.065), respectively]. Individuals who are young, patients with a history of severe acute exacerbations, farmers, smokers, and individuals admitted in cooler seasons may be particularly susceptible. Sensitivity analyses omitting COVID-19 cases showed barely significant associations for PM_2.5, PM₁₀ and NO₂, with CO displaying only a faint, non-significant relationship.

Conclusion: PM_2.5, PM₁₀, NO₂, and CO exposures were associated with COPD hospitalization in Kashi, precautionary measures should be taken with a focus on vulnerable subgroups, to control hospitalization for COPD associated with air pollutants.