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 FEV(1)/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 FEV(1)/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 > or =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 FEV(1)/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 FEV(1)/FVC ratio of <0.70 may identify at-risk patients, even among older adults.