Association Between Respiratory Exacerbations and Accelerated Lung Function Decline in Chronic Obstructive Pulmonary Disease: A Prospective Observational Population-based Cohort Study.

BACKGROUND: Moderate-to-severe and severe respiratory exacerbations in chronic obstructive pulmonary disease (COPD) accelerate lung function decline. However, whether any mild-to-severe exacerbations are associated with lung function decline in COPD remains unclear, especially in mild-to-moderate COPD and in the Global Initiative for Chronic Obstructive Lung Disease (GOLD) A. METHODS: The Early COPD (ECOPD) study was a 3-year, prospective cohort study conducted in China. Participants were diagnosed with COPD at baseline and had complete annual spirometry and exacerbation data from baseline to 3 years. Mild exacerbation was defined as an event treated domestically; moderate, treated as an outpatient; and severe, hospitalisation treatment. GOLD 2025 A was defined as COPD with few symptoms and without frequent exacerbations. Subgroup analyses were conducted in mild-to-moderate COPD and GOLD 2025 A. RESULTS: Of 915 patients with COPD at baseline in the ECOPD study, 703 (77%) had complete spirometry and exacerbation data each year during the 3-year follow-up and were included in the analysis. In COPD, patients with any mild-to-severe exacerbation had faster postbronchodilator forced expiratory volume in 1 second (FEV1) decline (adjusted difference 13 mL/year, 95% confidence interval [CI] 3-23, P = 0.015) and faster post-bronchodilator FEV1% predicted decline (adjusted difference 0.5%/year, 95% CI 0.1-0.9, P = 0.012) than those without. Results were generally consistent in direction in mild-to-moderate COPD and GOLD 2025 A. CONCLUSIONS: Any mild-to-severe exacerbation was associated with accelerated lung function decline in COPD, even in mild-to-moderate COPD and GOLD 2025 A. Any exacerbation in COPD should be considered in further disease management.