1. The presence of emphysema-like lung detected on computed tomography (CT) scans was associated with increased all-cause mortality in patients without obstructive lung disease.
2. This link was also associated with patient smoking status.
Evidence Rating Level: 2 (Good)
Study Rundown: Although obstructive lung diseases like emphysema are typically associated with smoking, there is a relatively high prevalence of emphysema among non-smokers. Emphysematous lung changes (i.e., emphysema-like lung) can be detected on computed tomography (CT) imaging, and are frequently found as incidental findings in smokers and non-smokers alike. However, its significance is unclear among patients without clinical evidence of obstructive lung disease. This study evaluated the relationship between mortality and CT-detected emphysema-like lung among patients without chronic obstructive pulmonary disease (COPD). Overall, the presence of emphysema-like lung was associated with increased all-cause mortality, and risk of death increased as the amount of emphysema-like lung increased. The association between emphysematous lung changes and increased mortality was particularly pronounced among current smokers. The primary limitation of this study arose from the type of imaging used; patients received cardiac, not pulmonary, CT scans, which typically cannot capture the uppermost portion of the lungs where emphysematous changes are most common. Additionally, the role of this evaluation in clinical practice is unclear, particularly since there are currently no mortality-reducing treatments for emphysema. Nevertheless, these results suggest that incidentally-detected emphysema-like lung may have negative implications for patients, even when those patients do not have clinical signs of obstructive lung disease.
In-Depth [prospective cohort]: This study analyzed CT scan and mortality data from 2,965 participants without COPD in the Multi-Ethnic Study of Atherosclerosis. Emphysema-like lung was detected on cardiac CT scan and was defined as a continuous variable computed from the number of air-density lung voxels normalized to total imaged lung voxels. After controlling for a number of potential confounders, emphysema-like lung was significantly, linearly associated with all-cause mortality when all patients were considered together, with an adjusted hazard ratio (aHR) of 1.14 (95% CI 1.04-1.24) per one-half interquartile range of emphysema-like lung. The effect was most pronounced among current smokers, less pronounced but statistically significant among former smokers, and trending upward, but not significantly, among never-smokers. However, addition of emphysema voxels to a predictive model based on other predictors of mortality (including smoking) only marginally increased the predictive value of the model (c-statistic increased from 0.786 to 0.791). Regardless, these results highlight the potentially adverse effects of sub-clinical emphysematous lung changes and highlight the need to develop new therapies to target this widespread disease.
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