Clinical characteristics and 2-year outcomes of chronic obstructive pulmonary disease patients with high blood eosinophil counts: a population-based prospective cohort study in China

Background: High blood eosinophil count (BEC) is a useful biomarker for guiding inhaled corticosteroid therapy in patients with chronic obstructive pulmonary disease (COPD), yet its implications in a community setting remain underexplored. This study aimed to elucidate the clinical characteristics and outcomes of COPD patients with high BEC within the Chinese community.Methods: We obtained baseline and 2-year follow-up data from COPD patients (post-bronchodilator forced expiratory volume in 1 second/forced vital capacity <0.70) in the Early COPD study. Patients with a BEC ≥300 cells/µL were classified as the high BEC group. We assessed differences in the clinical characteristics and outcomes between high and low BEC patients. Sensitivity analyses were conducted on COPD patients without a history of corticosteroid use or asthma.Results: Of the 897 COPD patients, 205 (22.9%) had high BEC. At baseline, high BEC patients exhibited a higher proportion of chronic respiratory symptoms, lower lung function, and more severe small airway dysfunction than low BEC patients. Over the 2-year period, high BEC patients experienced a significantly higher risk of acute exacerbations (relative risk: 1.29, 95% confidence interval: 1.09–1.49; P = 0.002), even after adjusting for confounders. No significant difference was observed in lung function decline rates. The sensitivity analysis yielded consistent results.Conclusions: COPD patients with high BEC in a Chinese community exhibited poorer health status, more severe small airway dysfunction, and a higher risk of exacerbations. Future research should explore the pathological mechanisms underlying the poorer prognosis in patients with high BEC.