• David A McAllister, Firas S Ahmed, John H M Austin, Claudia I Henschke, Brad M Keller, Adina Lemeshow, Anthony P Reeves, Sonia Mesia-Vela, G D N Pearson, Maria C Shiau, Joseph E Schwartz, David F Yankelevitz, and R Graham Barr.
• Centre for Population Health Sciences, University of Edinburgh, Edinburgh, United Kingdom; Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America.
• Plos One. 2014 Jan 1;9(4):e93221.

BackgroundEmphysema on CT is common in older smokers. We hypothesised that emphysema on CT predicts acute episodes of care for chronic lower respiratory disease among older smokers.Materials And MethodsParticipants in a lung cancer screening study age ≥ 60 years were recruited into a prospective cohort study in 2001-02. Two radiologists independently visually assessed the severity of emphysema as absent, mild, moderate or severe. Percent emphysema was defined as the proportion of voxels ≤ -910 Hounsfield Units. Participants completed a median of 5 visits over a median of 6 years of follow-up. The primary outcome was hospitalization, emergency room or urgent office visit for chronic lower respiratory disease. Spirometry was performed following ATS/ERS guidelines. Airflow obstruction was defined as FEV1/FVC ratio <0.70 and FEV1<80% predicted.ResultsOf 521 participants, 4% had moderate or severe emphysema, which was associated with acute episodes of care (rate ratio 1.89; 95% CI: 1.01-3.52) adjusting for age, sex and race/ethnicity, as was percent emphysema, with similar associations for hospitalisation. Emphysema on visual assessment also predicted incident airflow obstruction (HR 5.14; 95% CI 2.19-21.1).ConclusionVisually assessed emphysema and percent emphysema on CT predicted acute episodes of care for chronic lower respiratory disease, with the former predicting incident airflow obstruction among older smokers.

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