Difference in Mortality Risk in Elderly People with Bronchial Obstruction Diagnosed Using a Fixed Cutoff or the Lower Limit of Normal of the FEV1/FVC Ratio

Abstract

Background: Whether a fixed cutoff or the lower limit of normal of the FEV1/FVC ratio should be used to diagnose bronchial obstruction is still a matter of debate. This issue is particularly important for elderly people. Objectives: We used equations applicable up to 90 years of age to evaluate the mortality of elderly people diagnosed with bronchial obstruction using either a fixed cutoff of 0.7 or the lower limit of normal (LLN). Methods: Participants in the SaRA (Salute Respiratoria nell'Anziano, Italian for "Respiratory Health in the Elderly") study were grouped as follows: FEV1/FVC ≥0.7 and ≥ LLN (n = 535: F-/L-), FEV1/FVC <0.7 but ≥ LLN (n = 118: F+/L-), and FEV1/FVC <0.7 and < LLN (n = 229: F+/L+). We estimated the mortality risk in the three groups over 15 years of follow-up. Results: The mean age was 73 years (58% men). The hazard ratio (HR) for mortality was 1.427 (95% CI: 1.09-1.868) in the F+/L- group and 2.143 (95% CI: 1.13-1.995) in the F+/L+ group. After adjustment for potential confounders, we found no increased mortality in the F+/L- group (HR: 1.007, 95% CI: 0.755-1.342), while the HR in the F+/L+ group was still sizeable (1.474, 95% CI: 1.136-1.911). Conclusions: As expected, using a fixed cutoff translates in a larger number of people to be classified as having bronchial obstruction. In our sample the increased mortality in the F+/L- group is due to the confounding effect of age and sex. Our study lends support to the use of LLN in elderly people.