1. The presence of interstitial lung abnormalities was associated with a greater risk of all-cause mortality, independent of smoking, COPD, cancer, and coronary artery disease status.
Evidence Rating Level: 2 (Good)
Study Rundown: Interstitial lung disease (ILD) refers to a group of conditions characterized by progressive scarring of the lung tissue. Symptoms generally include decreased exercise capacity and shortness of breath caused by reductions in lung capacity and gas exchange. The etiology of ILD is understood in a subset of diseases—like occupational exposures and autoimmune disease—but most frequently unknown, such as in the case of idiopathic pulmonary fibrosis (IPF). Complications of IPF are severe and include respiratory failure, collapsed lung, and pulmonary hypertension. Previous investigations demonstrated that the presence of interstitial lung abnormalities on CT may signify early signs of pulmonary fibrosis. Thus this study set out to determine if interstitial lung abnormalities are associated with increased rates of mortality.
Interstitial lung abnormalities were found in 7-9% of adults studied, and the finding was associated with a greater risk of all-cause mortality. Importantly, the increased risk persisted when controlling for smoking, cancer, chronic obstructive pulmonary disease (COPD), and coronary artery disease (CAD). This study was well run, utilizing a large sample population and controlling for a variety of factors which may have otherwise affected the results. However, it may have been limited somewhat, considering its lack of cause of death information in three of the four cohorts, as well as the older median age of participants with ILD versus those without. Given the results of this study combined with the often asymptomatic nature of interstitial lung disease, future research should focus on reducing the mortality associated with ILD through screening while also increasing public awareness of the initial symptoms.
Relevant Reading: MUC5B promoter polymorphism and interstitial lung abnormalities
In-Depth [prospective cohort]: This prospective cohort study evaluated patients from 4 different cohorts; including 2633 participants from the Framingham Heart Study (FHS) between 2008 and 2011, 5320 from the Age Gene/Environment Susceptibility (AGES)-Reykjavik study between 2002 and 2006, 2068 from the COPDGene Study between 2007 and 2010, and 1670 from the Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE) study between 2005 and 2006. Interstitial lung abnormalities were present in 7-9% of all participants. There was a 6% absolute increase in the mortality rate among those with ILD compared to those without (CI95, 2%- 10%) in the FHS, a 23% increase (95% CI, 18%- 28%) in AGES-Reykjavik, a 5% increase (95% CI, −1%- 11%) in COPDGene, and a 6% increase (95% CI, 1%- 11%) in ECLIPSE. In the FHS, 6% of never smokers with interstitial lung abnormalities died compared to 0.3% of never smokers without interstitial abnormalities, a difference of 5.7% (95% CI, 1%-12%). In AGES-Reykjavik, 52% of never smokers with interstitial lung abnormalities died compared to 31% of those without interstitial lung abnormalities, a difference of 21%, (95% CI, 11%-31%).
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