Association between annual change in FEV1 and comorbidities or impulse oscillometry in chronic obstructive pulmonary disease

Abstract

Background: Chronic obstructive pulmonary disease (COPD) is characterized by persistent respiratory symptoms and airflow limitation. The decline in forced expiratory volume in one second (FEV₁) 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 FEV₁ 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 FEV₁ was associated with comorbidities and IOS parameters.

Results: The annual change in FEV₁ 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 FEV₁ and %FEV₁ 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.

Keywords: COPD Assessment Test; Chronic obstructive pulmonary disease; Impulse oscillometry system; Pulmonary function test; St. George’s Respiratory Questionnaire.

Fig. 1

Selection of participants. Of 97 patients diagnosed with COPD who were treated in the clinic between January 2012 and December 2015, 32 patients were excluded and 65 participated in this study

Fig. 2

Distribution of annual change in FEV₁ in patients with COPD_. According to observation over 5 years, the annual change in FEV₁ (mL) varied widely. The mean (SEM) was − 17.8 (4.0) mL/year (n = 65)

Fig. 3

Comparison of FEV₁ and %FEV₁ over time between current and former smokers with COPD. There were significant differences in FEV₁ (A) or %FEV₁ (B) between current and former smokers both 4 and 5 years after baseline. The bars represent mean ± standard error of the mean. The differences between current and former smokers were analyzed using unpaired t-tests. NS: not significant, *: p < 0.05, ** p < 0.01

Fig. 4

Comparison of %FEV₁ in COPD patients with and without comorbidities. There were significant differences in %FEV₁ in patients with and without pneumonia or asthma but not cancer or cardiovascular disease. The bars represent mean ± standard error of the mean. The differences between patients with and without each comorbidity were analyzed using unpaired t-tests. NS: not significant, *: p < 0.05, ** p < 0.01