Young and middle-aged adults with airflow limitation according to lower limit of normal but not fixed ratio have high morbidity and poor survival: A population-based prospective cohort study

Abstract

A presumed consequence of using a fixed ratio for the definition of airflow limitation (AFL) has been overdiagnosis among older individuals and underdiagnosis among younger individuals. However, the prognosis of younger individuals with potentially underdiagnosed AFL is poorly described. We hypothesised that potential underdiagnosis of AFL at a younger age is associated with poor prognosis. We assigned 95 288 participants aged 20-100 years from the Copenhagen General Population Study into the following groups: individuals without AFL with forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) ≥0.70 and ≥lower limit of normal (LLN) (n=78 779, 83%); individuals with potentially underdiagnosed AFL with FEV1/FVC ≥0.70 and <0.70 and ≥LLN (n=3088, 3%); and individuals with AFL with FEV1/ FVC <0.70 and