Occupation and Computed Tomography Measurements of Chronic Obstructive Pulmonary Disease

Abstract

Introduction Occupational exposures have been linked to the development of chronic obstructive pulmonary disease (COPD). However, there are no studies reporting associations between occupation and computed tomography (CT) measures of COPD, such as airway wall thickness and lung density. Methods We analyzed data from a cross-sectional hospital and population-based study of current and past smokers conducted in Bergen, Norway between 2003 and 2005. 951 subjects completed an occupational questionnaire and underwent chest CTs to evaluate lung density (% low attenuation areas - %LAA950) and airway wall thickness (AWT) as a measure of chronic bronchitis. An industrial hygienist assigned a categorical dust exposure measure, 0 (none, n=444), 1 (low, n=308), 2 (medium, n=129) or 3 (high, n=50), based on job title and work type. We assessed the relationship between dust exposure and CT measures using multivariable regression, adjusting for age, sex, smoking and percent total lung capacity (airway obstruction-adjusted) as a measure of breath hold on CT. Results When compared to no dust exposure, the three dust exposure categories had a 20% (0.99%, 46%), 54% (18%, 102%), and 33% (0.92%, 93%) increase in geometric mean %LAA950, respectively, after adjusting for covariates. This suggests more emphysematous change in the dust exposure categories. When testing the association between dust exposure and AWT, the other COPD phenotype, the high dust category had a mean 0.092mm (.002, .181) greater AWT compared to no dust exposure, after adjusting for covariates. Conclusion Dust exposure, as defined by occupational title and work type, was associated with more areas of low lung density, reflecting more lung emphysema. Lack of power in the high dust category limited the ability to detect a statistically significant dose-response relationship through all levels of dust exposure. The association of high dust exposure with airway wall thickness suggests that there is an association with chronic bronchitis at high dust levels only. Future studies using a job exposure matrix may allow more precise exposure estimation and quantification of the associations with CT measures of COPD.