Association between air pollution and acute exacerbation of chronic obstructive pulmonary disease in Hebei Province

Evidence regarding the short-term effects of ambient air pollution on acute exacerbations of chronic obstructive pulmonary disease (AECOPD) across multiple cities in northern China remains limited. This study aimed to evaluate the associations between major ambient air pollutants and AECOPD hospitalizations, as well as their lagged effects. We conducted an ecological time-series study of 14,786 AECOPD hospitalizations recorded at 49 hospitals in Shijiazhuang, Handan, and Chengde, Hebei Province, from January 1, 2018, to December 31, 2020. City-specific associations between daily concentrations of fine particulate matter (PM ₂ . ₅ ), inhalable particulate matter (PM ₁₀ ), sulfur dioxide (SO ₂ ), nitrogen dioxide (NO ₂ ), carbon monoxide (CO), and 8-hour ozone and AECOPD hospitalizations were estimated using distributed lag nonlinear models, with adjustment for long-term trends, temperature, relative humidity, day of the week, public holidays, and stages of the coronavirus disease 2019 pandemic. Single-day lag effects from lag 0 to lag 5, cumulative lag effects from lag 0–1 to lag 0–5, effects of extreme pollutant concentrations, and associations stratified by age and sex were evaluated. City-specific estimates were subsequently pooled using random-effects multivariate meta-analysis. Associations were expressed as relative risks with 95% confidence intervals. During the 1096-day study period, 14,786 AECOPD hospitalizations were recorded. Compared with the 25th-percentile concentrations, the 75th-percentile concentrations of PM _2.5 , PM ₁₀ , SO ₂ , NO ₂ , and CO generally showed stronger cumulative associations with longer lag periods, with the largest estimates usually observed at lag 0–5 days, whereas single-day effects were weak. All 6 pollutants exhibited nonlinear cumulative exposure–response relationships. Compared with median concentrations, the 99th-percentile concentrations of PM _2.5 , PM ₁₀ , SO ₂ , NO ₂ , and CO were associated with higher hospitalization risks. High PM _2.5 reached its maximum effect at lag 0–5 days (relative risk, 1.391; 95% confidence interval, 1.169–1.658). Higher 8-hour ozone concentrations were generally associated with lower hospitalization risk. Associations were more pronounced among adults aged ≥65 years and males. Short-term exposure to PM ₂ . ₅ , PM ₁₀ , SO ₂ , NO ₂ , and CO was associated with increased AECOPD hospitalization risk, with nonlinear, lagged, and cumulative effects. Older adults and females may be more susceptible to ambient air pollution.