Air pollution, inhaled therapy and COPD exacerbations in Yunlin, Taiwan: a 2016–2024 single-centre retrospective cohort with environmental and carbon-footprint analyses

Background Air pollution exacerbates chronic obstructive pulmonary disease (COPD), increasing hospitalisation and exacerbation rates. While inhaled therapy is a cornerstone of COPD management, pressurised metered-dose inhalers (pMDIs) significantly contribute to greenhouse gas (GHG) emissions. This study evaluates the interplay between air pollution exposure, inhaled therapy selection and COPD exacerbations to identify strategies that optimise clinical outcomes while reducing environmental impact. Methods A retrospective observational cohort study was conducted using COPD patient records (ICD-10: J44.0, J44.1, J44.8, J44.9) from the National Taiwan University Hospital Yunlin Branch (2016–2024). Patient visits, including outpatient, emergency and inpatient admissions, were analysed alongside air pollution data (PM_2.5, PM₁₀, NO₂, O₃, CO) from the Environmental Protection Administration. Regression models assessed the impact of inhaled therapies, short-acting β₂-agonists (SABAs), long-acting β₂-agonists (LABAs), long-acting muscarinic antagonists (LAMAs) and triple therapy (ICS/LABA/LAMA), on exacerbation rates and inhaler-associated carbon emissions. Results Higher PM_2.5 levels correlated with a 0.97% increase in COPD exacerbation rates (B=0.0291, p=0.0001). Triple therapy was significantly associated with reduced exacerbations (B=−0.0035, p=0.0003), whereas higher SABA use was associated with markers of poorer COPD control (B=7.145, p<0.001). The uptake of non-pMDIs, such as dry powder inhalers and soft mist inhalers, rose in 2020–2021 as hospitalisations declined. In 2022–2024, pMDI use and estimated emissions increased, while emergency room (ER) visits were unchanged and hospitalisations declined modestly. A 42% increase in non-pMDI prescriptions in 2020–2021 was associated with a decline in hospitalisations and emissions. However, a subsequent shift back to pMDIs in 2022–2024 coincided with an increase in exacerbations and increased carbon footprint. Conclusion In this single-centre retrospective study, higher ambient PM_2.5 was associated with higher COPD acute exacerbation (AE) rates, and greater use of triple therapy correlated with lower hospitalisations. Our inhaler carbon-footprint estimates quantify GHG differences between device types but were not linked to AE and should inform sustainability discussions rather than clinical effectiveness.