Longitudinal changes in forced expiratory volume in 1 s in patients with eosinophilic chronic obstructive pulmonary disease

BACKGROUND: Data on changes in lung function in eosinophilic chronic obstructive pulmonary disease (COPD) are limited. We investigated the longitudinal changes in forced expiratory volume in 1 s (FEV(1)) and effects of inhaled corticosteroid (ICS) in Korean COPD patients. METHODS: Stable COPD patients in the Korean COPD subgroup study (KOCOSS) cohort, aged 40 years or older, were included and classified as eosinophilic and non-eosinophilic COPD based on blood counts of eosinophils (greater or lesser than 300 cells/μL). FEV(1) changes were analyzed over a 3-year follow-up period. RESULTS: Of 627 patients who underwent spirometry at least twice during the follow up, 150 and 477 patients were classified as eosinophilic and non-eosinophilic, respectively. ICS-containing inhalers were prescribed to 40% of the patients in each group. Exacerbations were more frequent in the eosinophilic group (adjusted odds ratio: 1.49; 95% confidence interval: 1.10–2.03). An accelerated FEV(1) decline was observed in the non-eosinophilic group (adjusted annual rate of FEV(1) change: − 12.2 mL/y and − 19.4 mL/y for eosinophilic and non-eosinophilic groups, respectively). In eosinophilic COPD, the adjusted rate of annual FEV(1) decline was not significant regardless of ICS therapy, but the decline rate was greater in ICS users (− 19.2 mL/y and − 4.5 mL/y, with and without ICS therapy, respectively). CONCLUSIONS: The annual rate of decline in FEV(1) was favorable in eosinophilic COPD compared to non-eosinophilic COPD, and ICS therapy had no beneficial effects on changes in FEV(1). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12890-022-01873-8.