Association between annual change in FEV(1) and comorbidities or impulse oscillometry in chronic obstructive pulmonary disease

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is characterized by persistent respiratory symptoms and airflow limitation. The decline in forced expiratory volume in one second (FEV(1)) is considered to be one of the most important outcome measures for evaluating disease progression. However, the only intervention proven to improve COPD prognosis is smoking cessation. This study therefore investigated the factors associated with annual FEV(1) decline in COPD. METHODS: This retrospective study followed up 65 patients treated for COPD for 5 years: 13 current smokers and 52 former smokers, 25 with pneumonia, 24 with asthma, 18 with cancer, and 17 with cardiovascular disease. The patients were divided into groups based on clinical cutoff parameters of the impulse oscillometry system (IOS): 11 high and 54 low R5, 8 high and 57 low R20, 21 high and 44 low R5–R20, 26 high and 39 low X5, 38 high and 27 low Fres, and 36 high and 29 low AX. We investigated whether the decline in FEV(1) was associated with comorbidities and IOS parameters. RESULTS: The annual change in FEV(1) over 5 years was significantly affected by smoking status (current − 66.2 mL/year vs. former − 5.7 mL/year, p < 0.01), pneumonia (with − 31.5 mL/year vs. without − 8.9 mL/year, p < 0.05), asthma (with − 30.2 mL/year vs. − 10.8 mL/year, p < 0.01), but not by cancer and cardiovascular disease. In the groups defined by IOS results, only the high AX group had significantly more annual decline in FEV(1) and %FEV(1) than the low AX group (− 22.1 vs. − 12.8, p < 0.05 and − 0.20 vs. 0.40, p < 0.05, respectively). CONCLUSIONS: Continuing smoking as well as complications in pneumonia and asthma would be risk factors for the progression of COPD. AX might be a suitable parameter to predict the prognosis of patients with COPD. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12890-022-01980-6.