Supernormal lung function and risk of COPD: A contemporary population-based cohort study

Background: Investigation of the natural history of chronic obstructive pulmonary disease (COPD) has led to the recognition that individuals with higher than normal lung function may have lower risk of developing COPD. We tested the hypothesis that individuals with supernormal lung function have lower risk of COPD. Methods: We followed 108,246 adults from the Copenhagen General Population Study recruited between 2003 and 2015 for clinical COPD outcomes until 2018. A subset of 16,892 attended another examination approximately 10 years later, allowing to investigate lung function decline and COPD development (forced expiratory volume in 1 se (FEV1/forced vital capacity (FVC)<0.70 and FEV1 <80% predicted with chronic respiratory symptom). Supernormal lung function was defined as FEV1 >upper limit of normal (ULN). Findings: At baseline, 3944(4%) had supernormal lung function, 91,938(85%) normal lung function, and 12,364(11%) had below normal lung function. Individuals with baseline supernormal versus normal lung function had higher FEV1 decline but did not differ in FEV1/FVC decline. None had COPD at 10 years in those with supernormal lung function, while 3% had in those with normal lung function. Early-life risk factors associated with COPD development and smoking exposure in different stages of life were less common in individuals with supernormal lung function. Compared to individuals with normal lung function, multivariable adjusted hazard ratios in those with supernormal lung function were 0.19(95% confidence interval:0.08-0.46) for acute obstructive lung disease hospitalisations, 0.56(0.45-0.69) for pneumonia hospitalisations, and 0.81(0.72-0.91) for all-cause mortality. Interpretation: Supernormal lung function is associated with lower risk of developing COPD. (C) 2021 The Author(s). Published by Elsevier Ltd.