FEV ₁ is a stronger mortality predictor than FVC in patients with moderate COPD and with an increased risk for cardiovascular disease

Abstract

Purpose

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of death worldwide. Impaired lung function is associated with heightened risk for death, cardiovascular events, and COPD exacerbations. However, it is unclear if forced expiratory volume in one second (FEV ₁) and forced vital capacity (FVC) differ in predictive value.

Patients and Methods

Data from 16,485 participants in the Study to Understand Mortality and Morbidity (SUMMIT) in COPD were analyzed. Patients were grouped into quintiles for each lung function parameter (FEV ₁ %predicted, FVC %predicted, FEV ₁/FVC). The four highest quintiles (Q2–Q5) were compared to the lowest (Q1) to assess their relationship with all-cause mortality, cardiovascular events, and moderate-to-severe and severe exacerbations. Cox-regression was used, adjusted for age, sex, ethnicity, body-mass index, smoking status, previous exacerbations, cardiovascular disease, treatment, and modified Medical Research Council dyspnea score.

Results

Compared to Q1 (<53.5% FEV ₁ predicted), increasing FEV ₁ quintiles (Q2 53.5–457.5% predicted, Q3 57.5–461.6% predicted, Q4 61.6–465.8% predicted, and Q5 ≥65.8%) were all associated with significantly decreased all-cause mortality (20% (4–34%), 28% (13–40%), 23% (7–36%), and 30% (15–42%) risk reduction, respectively). In contrast, a significant risk reduction (21% (4–35%)) was seen only between Q1 and Q5 quintiles of FVC. Neither FEV ₁ nor FVC was associated with cardiovascular risk. Increased FEV ₁ and FEV ₁/FVC quintiles were also associated with the reduction of moderate-to-severe and severe exacerbations while, surprisingly, the highest FVC quintile was related to the heightened exacerbation risk (28% (8–52%) risk increase).

Conclusion

Our results suggest that FEV ₁ is a stronger predictor for all-cause mortality than FVC in moderate COPD patients with heightened cardiovascular risk and that subjects with moderate COPD have very different risks.