Association between outdoor air pollutants and risk of acute exacerbation of chronic obstructive pulmonary disease in Xi’an, China

Attention has been paid to the association between outdoor air pollutants and acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Xi’an has special basin topography and meteorological conditions as well as developed industries. All these make the outdoor air pollution in Xi 'an serious. Thus, we wish to assess the association between outdoor air pollutants and AECOPD in Xi’an, China. Daily AECOPD inpatient and outpatient visits in 2018 were collected from the eight first-class large general hospitals at grade 3. Data on pollutants and weather conditions in Xi 'an from January 1 to December 31, 2018 were accessed from Xi 'an Environmental Protection Bureau and Xi 'an Meteorological Bureau. Spearman rank correlation, linear regression, and generalized additive models were used for data analysis. Outdoor air pollutants (PM10, PM2.5, SO₂, NO₂, and CO) increase the risk of AECOPD. The impact of air pollutants on AECOPD patients has a hysteresis effect. PM10, PM2.5, CO, and NO₂ are associated with acute exacerbation in female COPD patients. PM10, PM2.5, CO, SO₂, and NO₂ are associated with acute exacerbation in old COPD patients (70 < age ≤ 80 years old). CO is associated with acute exacerbation in COPD Patients with eosinophils absolute count ≥ 300/μL. PM10 is associated with acute exacerbation in COPD patients with eosinophils absolute count < 100/μL. Exposure to PM10, PM2.5, SO₂, NO₂, and CO is positively associated significantly with hospital visits for AECOPD in Xi’an. Various air pollutants have different associations with different types of AECOPD patients. The relationship between O₃ and AECOPD still needs to be further explored.