Occupational exposures and progression of emphysema on computed tomography in the Multi-Ethnic Study of Atherosclerosis Lung Study

Abstract

Importance: While occupational exposure to vapors, gases, dust, and fumes (VGDF) is arecognized contributor to airflow limitation that defines chronic obstructive pulmonary disease (COPD), the impact of VGDF exposure on the longitudinal progression of emphysema as measured by computed tomography (CT) has not been well studied. Objective: To determine the association of occupational exposures with progression of percent emphysema as measured by CT scan in a multi-ethnic, longitudinal population-based sample. Methods: The Multi-Ethnic Study of Atherosclerosis (MESA) is a prospective cohort study that recruited community-dwelling US adults, ages 45-84 without known cardiovascular disease in 2000 and 2002, from six US regions. Occupational exposures to VGDF were assessed via the National Institute for Occupational Safety and Health COPD Job Exposure Matrix (NIOSH COPD JEM) and, in a subset, self-report using the standardized VGDF questionnaires. Percent emphysema was assessed as the percent of lung voxels less than -950HU on the lung windows of cardiac CT scans performed in MESA exams 1-4 (2000-2007) and full-lung CTs performed in MESA exams 5-6 (2010-18). Participants with valid occupation information, emphysema data, a baseline cardiac CT scan, and at least one follow-up CT scan were included in this study analysis. Linear mixed models, including a random effect for participant in addition to interactions between occupational exposure and time (occupational exposure x time), were used to assess the association between occupational exposures and progression of percent emphysema. Models were adjusted for sociodemographic covariates and tobacco use. Results: Among the 6,430 participants, mean age at recruitment was 62 [standard deviation 10.2] years, 49% were male. Median follow-up was 9.7 [interquartile range 12.1] years. JEM- assigned exposure to VGDF was low in 66% (N = 4249), medium in 22% (N = 1415), and high in 12% (N = 766) of participants. In comparison to the low exposure group, medium and high exposure groups had faster emphysema progression (medium exposure: 0.25 [95% confidence interval (CI): 0.06, 0.43]; high exposure: 0.33 [CI: 0.09, 0.58]; p<0.01) over 10 years. Of 3929 participants with self-reported VGDF data, 43% (N = 1709) reported ever exposure to VGDF. Self-reported, ever exposure to VGDF was also significantly associated with a progression in percent emphysema (0.23 [CI: 0.06, 0.40]; p<0.01) over 10 years. Conclusion: In this large prospective cohort study with long-term CT scanning, both JEM- assigned and self-reported occupational exposure to VGDF were significantly associated with progression of quantitively assessed emphysema.