Defining chronic obstructive pulmonary disease in older persons

Abstract

Objective: To develop a more age-appropriate spirometric definition of chronic obstructive pulmonary disease (COPD) among older persons.

Methods: Using data from the Third National Health and Nutrition Examination Survey (NHANES III), we developed a two-part spirometric definition of COPD in older persons, aged 65-80 years, that 1) determines a cut-point for the ratio of forced expiratory volume in 1 s to forced vital capacity (FEV1/FVC) based on mortality risk; and 2) among persons below this critical FEV1/FVC threshold, determines cut-points for the FEV1, expressed as a standardized residual percentile (SR-tile) and based on the prevalence of respiratory symptoms and mortality risk. Measurements included spirometry, health questionnaires, and mortality (National Death Index).

Results: There were 2480 older participants with a mean age of 71.7 years; 1372 (55.4%) had a smoking history, 1097 (44.2%) had respiratory symptoms and, over the course of 12-years, 868 (35.0%) had died. Among participants with an FEV1/FVC<.70 and FEV1<5th SR-tile, representing 7.7% of the cohort, the risk of death was doubled (adjusted hazard ratio, 2.01; 95% confidence interval [CI], 1.60-2.54). Among participants with an FEV1/FVC<.70 and FEV1<10th SR-tile, representing 13.4% of the cohort, the prevalence of respiratory symptoms was elevated (adjusted odds ratio, 2.44; CI, 1.79-3.33).

Conclusion: In a large, nationally representative sample of community-living older persons, defining COPD based on an FEV1/FVC<.70, with FEV1 cut-points at the 10th and 5th SR-tiles, identifies individuals with an increased prevalence of respiratory symptoms and an increased risk of death, respectively.

Figure 1. Kaplan-Meier survival curves in participants with airflow limitation, stratified by FEV1 SR-tile

Airflow limitation was established by an FEV1/FVC < .70, with severity defined by FEV1 SR-tile. The number of participants at risk in the FEV1 groups of < 5^th, 5–9^th, 10–29^th, 30–49^th, and ≥ 50^th SR-tile was 179, 133, 281, 122, and 116, respectively, for a total of 831. The referent group, which included 1,488 participants, had normal pulmonary function defined by an FEV1/FVC ≥ .70 and an FVC ≥ lower limit of normal. Abbreviations: FEV1= forced expiratory volume in 1 second; FVC= forced vital capacity; SR-tile= standardized residual percentile.