Late Breaking Abstract - Longitudinal progression of emphysema-like lung on CT in a general population study

Introduction: Emphysema is defined on pathology, however it can also be identified on CT scan where it has been associated with increased all-cause mortality in those with and without COPD. Determinants of emphysema progression in the general population have not been extensively studied. Methods: A large population-based study enrolled participants 45-84 years old in 2000-02 in six U.S. cities. The percent of emphysema-like lung was defined on outside-air corrected computed tomoraphy (CT) scans as the area with attenuation below -950 Hounsfield Units. Percent emphysema was measured up to 5 times in each participant on cardiac (2000-07) and full-lung CTs (2010-18). Results: At baseline the 7069 participants with at least 1 measure of percent emphysema were 62±10 years old, 47% male and 45% were never smokers. Mean follow up time was 9.6±10 years (range 1-18 years) with a median of 3 CT scans each. Percent emphysema increased 0.58 percentage points on average over 10 years (95% CI: 0.39, 0.78, P-value <0.001). Percent emphysema progressed faster for each pack year of cigarettes smoked prior to the baseline visit (0.004%/pack year over 10 years, 95% CI 0.0002, 0.007, P-value = 0.036), for those with a lower BMI at baseline (-0.04 %/kg/m2; 95% CI -0.07, -0.02, P-value = 0.001), for women compared to men (1.09%/10 years, 95% CI 0.96, 1.22, P-value <0.001). Conclusions: In a general population cohort study, the percent of emphysema-like lung on CT was found to progress faster with increasing pack years of smoking cigarettes, for those with a lower BMI and for women compared to men. These insights into emphysema progression may help to identify high risk groups for further study of disease pathogenesis.