Indexed on: 20 Oct '18Published on: 20 Oct '18Published in: Annals of the American Thoracic Society
Quantitative computed tomography (CT) imaging can aid in COPD phenotyping. Few studies have identified whether occupational exposures are associated with distinct CT imaging characteristics. To examine the association between occupational exposures and CT-measured patterns of disease in the Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS). Participants underwent whole-lung multidetector helical CT at full inspiration and expiration. The association between occupational exposures (self-report of exposure to vapors, gas, dust, or fumes (VGDF) at the longest job) and CT metrics of emphysema (percent of total voxels < -950 HU at total lung capacity), large airways (wall area percent (WAP) and Pi10); small airways (% air trapping (percent total voxels < -856 HU at residual volume) and parametric response mapping of functional small airway abnormality (PRM fSAD)); and were explored using multivariate linear regression, and for central airway measures, generalized estimating equations to account for multiple measurements per individual. Models were adjusted for age, gender, race, current smoking status, pack years of smoking, body mass index, and site. Airways measurements were additionally adjusted for total lung volume. 2,736 participants with available occupational exposure data (n=927 without airflow obstruction and 1,809 with COPD) were included. Mean age was 64 years, 78% were white, and 54% male. 40% reported current smoking, and mean (SD) pack years was 49.3(26.9). Mean (SD) post-bronchodilator FEV1 was 73(27)% predicted. 49% reported VGDF exposure. VGDF exposure was associated with higher emphysema (beta=1.17, CI (0.44, 1.89)), greater large airway disease as measured by WAP (segmental beta=0.487, CI (0.320, 0.654)); subsegmental beta=0.400, CI (0.275, 0.527)), and Pi10 (beta=0.008, CI (0.002, 0.014)), and with greater small airway disease as measured by air trapping (beta=2.60, CI (1.11, 4.09)), and nominally associated with an increase in PRM fSAD (beta=1.45, CI (0.31, 2.60)). These findings correspond to higher odds of percent emphysema, WAP, and air trapping above the 95th percentile of measurements in non-smoking controls in individuals reporting VGDF exposure. In an analysis of SPIROMICS participants, we found that VGDF exposure in the longest job was associated with an increase in emphysema, and large and small airway disease as measured by quantitative CT imaging.