Lung-Function Trajectories Leading to Chronic Obstructive Pulmonary Disease

TLDR

COPD may arise from an accelerated decline in FEV1, but a normal decline can also lead to COPD when baseline FEV1 is below population norms. The authors stratified participants in three cohorts by baseline FEV1 (≥80% vs <80%) and COPD status at follow‑up, then measured FEV1 decline over approximately 22 years. Among individuals with low baseline FEV1, 26% developed COPD versus 7% among those with normal baseline; roughly half of COPD cases had normal baseline FEV1 but a rapid decline (~53 ml/yr), while the other half had low baseline and a slower decline (~27 ml/yr). The study was funded by an unrestricted grant from GlaxoSmithKline and others.

Abstract

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is thought to result from an accelerated decline in forced expiratory volume in 1 second (FEV1) over time. Yet it is possible that a normal decline in FEV1 could also lead to COPD in persons whose maximally attained FEV1 is less than population norms. METHODS: We stratified participants in three independent cohorts (the Framingham Offspring Cohort, the Copenhagen City Heart Study, and the Lovelace Smokers Cohort) according to lung function (FEV1 ≥80% or <80% of the predicted value) at cohort inception (mean age of patients, approximately 40 years) and the presence or absence of COPD at the last study visit. We then determined the rate of decline in FEV1 over time among the participants according to their FEV1 at cohort inception and COPD status at study end. RESULTS: Among 657 persons who had an FEV1 of less than 80% of the predicted value before 40 years of age, 174 (26%) had COPD after 22 years of observation, whereas among 2207 persons who had a baseline FEV1 of at least 80% of the predicted value before 40 years of age, 158 (7%) had COPD after 22 years of observation (P<0.001). Approximately half the 332 persons with COPD at the end of the observation period had had a normal FEV1 before 40 years of age and had a rapid decline in FEV1 thereafter, with a mean (±SD) decline of 53±21 ml per year. The remaining half had had a low FEV1 in early adulthood and a subsequent mean decline in FEV1 of 27±18 ml per year (P<0.001), despite similar smoking exposure. CONCLUSIONS: Our study suggests that low FEV1 in early adulthood is important in the genesis of COPD and that accelerated decline in FEV1 is not an obligate feature of COPD. (Funded by an unrestricted grant from GlaxoSmithKline and others.).