FEV1 decline is accelerated in only a minority of patients with COPD: a factorial analysis of longitudinal data

Background: Decline in forced expiratory volume in 1 sec (FEV1) is a characteristic of disease progression in COPD. Previous studies have shown that FEV1 longitudinal evolution is heterogeneous. Objective: To identify and characterize COPD patients with accelerated FEV1 decline. Methods: Among 1558 patients with COPD in a French multicenter cohort (Initiatives BPCO), patients were included when they had available longitudinal follow-up with ≥3 spirometry tests over a period of at least 2 years. Multiple descriptors of FEV1 evolution were subjected to principal component analysis (PCA) followed by hierarchical cluster analysis. Results: 479 patients with 3449 spirometry tests were studied. PCA identified two axes, accounting for 73% of the global variance. Cluster analysis based on these two axes identified two subgroups of patients. The first (Group 1, n=389, 81.2%) contained patients with limited or no FEV1 decline (median, IQR; -28 [-59; +1.5] ml/year) whereas the second (Group 2, n=90; 18.8%) contained patients with accelerated decline in FEV1 (-94 [-134; -64] ml/year). In multivariable logistic regression, characteristics associated with higher risk of belonging to Group 2 included male sex and higher FEV1 at baseline whereas higher mMRC and older age were associated with decreased risk. No significant difference in all-cause mortality was identified between the Group 1 and Group 2 (all-cause mortality 15.7% vs. 17.8%, respectively). Conclusion: In this hospital-based cohort of patients with COPD, accelerated decline in FEV1 occurred in less than 20% of patients, confirming that COPD is not a progressive disease in most patients.