Association between emphysema-like lung on cardiac computed tomography and mortality in persons without airflow obstruction

Background: Low lung function is known to predict mortality in the general population, but the prognostic significance of emphysema on computed tomography (CT) in persons without chronic obstructive pulmonary disease (COPD) is uncertain. Objective: To determine whether greater emphysema-like lung on CT is associated with all-cause mortality among persons in the general population without airflow obstruction or COPD. Design: Prospective cohort study. Setting: Population-based, multiethnic sample from 6 U.S. communities. Participants: 2965 participants aged 45 to 84 years without airflow obstruction on spirometry. Measurements: Emphysema-like lung was defined as the number of lung voxels with attenuation less than -950 Hounsfield units on cardiac CT and was adjusted for the number of total imaged lung voxels. Results: Among 2965 participants, 50.9% of whom had never smoked, there were 186 deaths over a median of 6.2 years. Greater emphysema-like lung was independently associated with increased mortality (adjusted hazard ratio per one-half interquartile range, 1.14 [95% CI, 1.04 to 1.24]; P = 0.004) after adjustment for potential confounders, including cardiovascular risk factors and FEV₁. Generalized additive models supported a linear association between emphysema-like lung and mortality without evidence for a threshold. The association was of greatest magnitude among smokers, although multiplicative interaction terms did not support effect modification by smoking status. Limitations: Cardiac CT scans did not include lung apices. The number of deaths was limited among subgroup analyses. Conclusion: Emphysema-like lung on CT was associated with allcause mortality among persons without airflow obstruction or COPD in a general population sample, particularly among smokers. Recognition of the independent prognostic significance of emphysema on CT among patients without COPD on spirometry is warranted.