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University of Kentucky, Lexington, KY
PURPOSE: The Global Initiative on Obstructive Lung Disease (GOLD) stages for the definition of chronic obstructive pulmonary disease (COPD) uses a fixed ratio of the post-bronchodilator forced expiratory volume in one second (FEV1)/ 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. Our objective was to determine morbidity and mortality among older adults whose FEV1/FVC is less than 0.70 but greater than the lower limit of normal (LLN).
METHODS: We classified the severity of COPD in 4,965 participants age 65 years and older in the Cardiovascular Health Study using these two methods and determined the age-adjusted proportion of the population that died or had a COPD-related hospitalization in up to 11 years of follow-up.
RESULTS: 1621(32.6%) subjects died and 935 (18.8%) had at least one COPD-related hospitalization during the follow-up period. People whose FEV1/FVC fell between the LLN and the fixed ratio had an increased adjusted risk of death (hazard ratio [HR] 1.3, 95% confidence interval [CI] 1.1, 1.5) and COPD-related hospitalization (HR 2.6, 95% CI 2.0, 3.3) during follow-up.
CONCLUSION: In this elderly cohort, subjects classified as "normal" using the LLN but abnormal using the fixed ratio were more likely to die and have a COPD-related hospitalization during follow-up.
CLINICAL IMPLICATIONS: The concern about "over-diagnosis" using the fixed ratio that stems from cross-sectional data deserves closer scrutiny from cohort studies.
DISCLOSURE: David Mannino, None.
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