Association between short-term ambient air pollution and outpatient visits for acute exacerbation of chronic obstructive pulmonary disease in Lanzhou, 2013-19.

Evidence between air pollution and hospital visits for acute exacerbation of chronic obstructive pulmonary disease (AECOPD) is inconsistent and limited in China. In this study, we constructed a time-series study to evaluate the association between air pollution and AECOPD outpatient visits. Daily hospital outpatient visits for AECOPD in three top level hospitals in Lanzhou from January 2013 to December 2019, as well as the air pollutants and meteorological data in the same period, were collected. Then, generalized additive models with quasi-Poisson regression were utilized to estimate the associations with single-day lags from lag0 to lag7 and cumulative-day lag from lag01 to lag07. For example, lag0 referred to the concentration of air pollutants at the current day and lag1 referred to the previous-day air pollutant concentration and so on. Lag01 meant the average concentration of air pollutants at the current and previous day, and lag07 corresponded to the eight-day moving average value of the current and previous 7 days. In addition, stratified analyses were performed by gender, age, and season. The risk estimates were expressed in terms of the percentage changes (PC) in AECOPD outpatient visits per 10 µg/m increment of air pollutants (except that CO was per 1 mg/m) and their respective 95% confidence intervals (CIs). The strongest effect on AECOPD morbidity was found lag07 for PM (PC = 1.96, 95% CI 1.07, 2.86 per 10 μg/m), lag03 for PM (PC = 0.25, 95% CI 0.01, 0.49 per 10 μg/m), lag05 for SO (PC = 1.67, 95% CI 0.54, 3.93 per 10 μg/m), and lag03 for NO (PC = 1.37, 95% CI 0.25, 2.51 per 10 μg/m). No significant association of O and CO with AECOPD onset was found. In the subgroup analyses, the associations of PM and SO were more pronounced on males than female, the patients aged < 65 years were more vulnerable to PM and NO, but 65-74 years old were more vulnerable to PM, SO, and NO. Patients aged ≥ 75 years suffered more from PM, PM, and SO. The associations between PM, PM, SO, NO, and AECOPD outpatients were stronger in the cold season than those in the hot season. From exposure-response curves, we observe linear relationships of PM, SO, NO, O8h, and CO with hospital outpatient visits for AECOPD. The increase in PM, PM, SO, and NO concentration will lead to an increase in the number of outpatient visits for AECOPD and have different influence patterns in different genders, ages, and seasons.