Chronic obstructive pulmonary disease in the older adult: What defines abnormal lung function?

Background: The Global Initiative on Obstructive Lung Disease stages for chronic obstructive pulmonary disease (COPD) uses a fixed ratio of the post-bronchodilator forced expiratory volume in 1 second (FEV ₁)/forced vital capacity (FVC) of 0.70 as a threshold. Since the FEV₁/FVC ratio declines with age, using the fixed ratio to define COPD may "overdiagnose" COPD in older populations. Objective: To determine morbidity and mortality among older adults whose FEV₁/FVC is less than 0.70 but more than the lower limit of normal (LLN). Methods: The severity of COPD was classified in 4965 participants aged ≥65 years in the Cardiovascular Health Study using these two methods and the age-adjusted proportion of the population who had died or had a COPD-related hospitalisation in up to 11 years of follow-up was determined. Results: 1621 (32.6%) subjects died and 935 (18.8%) had at least one COPD-related hospitalisation during the follow-up period. Subjects (n = 1134) whose FEV₁/FVC fell between the LLN and the fixed ratio had an increased adjusted risk of death (hazard ratio (HR) 1.3, 95% CI 1.1 to 1.5) and COPD-related hospitalisation (HR 2.6, 95% CI 2.0 to 3.3) during follow-up compared with asymptomatic individuals with normal lung function. Conclusion: In this cohort, subjects classified as "normal" using the LLN but abnormal using the fixed ratio were more likely to die and to have a COPD-related hospitalisation during follow-up. This suggests that a fixed FEV₁/FVC ratio of <0.70 may identify at-risk patients, even among older adults.