Occupational organic dust exposure and risk of chronic obstructive pulmonary disease (COPD) in Denmark

Background: COPD is a leading cause of death worldwide. Organic dust exposure is suggested to cause COPD. Occupational exposure to organic dust is common among farmers and wood workers. Aims and Objectives: To investigate the exposure-response relations between cumulative occupational organic dust exposure among Danish farmers and woodworkers and risk of COPD. Methods: We included all born in Denmark between 1950 and 1977, ever employed in farming or wood industry based on employment information on industry from the Supplementary Pension Fund Register (n=335,661). Cumulative organic dust levels were obtained by linking personal work histories (1964-2007) with 2 time-dependent Job Exposure Matrices based on 1) 500 personal dust measurements in Danish farmers and 2) aggregated WOODEX data with > 35,000 measurements from the wood industry. Incident COPD cases during follow-up (1997-2014) were identified by ICD-10 codes from the National Patient Register. We used discrete-time hazard analysis with person years as the unit of analysis and adjusted for age, sex, and calendar year. Smoking histories were available for 2,411 participants. Results: Cumulative organic dust exposure was inversely associated to COPD risk with ORadj (95% CI) of 0.96 (0.89-1.04), 0.79 (0.73-0.86), and 0.56 (0.51-0.62) for 2nd, 3rd, and 4th exposure quartiles compared to 1st. Sensitivity analysis suggested smoking as a strong predictor for COPD. Associations between smoking and cumulative dust exposure were weak. Conclusions: The results contradict previous findings, and may be explained by for example healthy worker survivor effect. Analysis adjusted for e.g. labor market attachment will be presented at the conference.