Short-term exposure to ambient air pollution and pneumonia hospital admission among patients with COPD: a time-stratified case-crossover study

Background Pneumonia is a major contributor to hospital admission for patients with chronic obstructive pulmonary disease (COPD). However, evidence for acute effects of ambient air pollution exposure on pneumonia hospital admission among patients with COPD is scarce. We aimed to examine the association between short-term exposure to ambient air pollution and pneumonia hospital admission among patients with COPD. Methods We enrolled COPD cases aged >= 60 years old and further filtered those who were admitted into hospitals from pneumonia during 2016-2019 in Guangdong province, China for main analysis. A time-stratified case-crossover design was applied to investigate the association and conditional logistic regression model was used for data analysis. We performed inverse distance weighting method to estimate daily individual-level exposure on particulate matter with an aerodynamic diameter <= 2.5 mu m (PM2.5), particulate matter with an aerodynamic diameter <= 10 mu m (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O-3) based on personal residential addresses. Results We included 6473 pneumonia hospital admissions during the study period. Each interquartile range (IQR) increase in PM2.5 (lag 2; IQR, 22.1 mu g/m(3)), SO2 (lag 03; IQR, 4.2 mu g/m(3)), NO2 (lag 03; IQR, 21.4 mu g/m(3)), and O-3 (lag 04; IQR, 57.9 mu g/m(3)) was associated with an odds ratio in pneumonia hospital admission of 1.043 (95% CI: 1.004-1.083), 1.081 (95% CI: 1.026-1.140), 1.045 (95% CI: 1.005-1.088), and 1.080 (95% CI: 1.018-1.147), respectively. Non-linear trends for PM2.5, PM10, and SO2 were observed in the study. Sex, age at hospital admission, and season at hospital admission did not modify the associations. Conclusions We found significantly positive associations of short-term exposure to PM2.5, SO2, NO2, and O-3 with pneumonia hospital admission among COPD patients. It provides new insight for comprehensive pneumonia prevention and treatment among COPD patients.