Occupational exposure and 4-year incidence of COPD among 45-84-year old Danes

Introduction: In COPD the population attributable fraction due to occupational exposure is about 15%, although longitudinal data from occupational exposure in population-based studies are sparse. Aims and objectives: The aim was to explore the impact of occupational exposure on the development of COPD in a longitudinal population-based study. Methods: A stratified sampling was conducted among 155 general practitioners. The 4-year follow-up included 1837 men and 914 women with a follow-up rate of 58%. Information about smoking, occupations and years of occupational exposures were obtained from questionnaires. Occupations were coded according to the Danish adaptation of The International Standard Classification of Occupations, revision 1988. Exposures to vapour, gas, dust, and fume (VGDF) in each occupation were evaluated by two independent specialists in occupational medicine. Exposures were divided in no, low, medium, and high exposure as 0, th centile lower limit of normal of FEV 1 and FEV 1 /FVC and analysed in a mixed Poisson regression. Results: At least 1 occupation with VGDF exposure was reported by 46% in their lifetime. The adjusted COPD incidence rate ratio (IRR) was associated with occupational exposure especially for low VGDF and organic dust exposure; IRR=3.71 (95% CI 1.17 to 11.8) and IRR=3.24 (95% CI 1.07 to 9.83), respectively, although no clear exposure-response relation was revealed. Additional adjustment for asthma status strengthens the association. However, by defining COPD according to the GOLD criteria no significant association was identified. Conclusion: Occupational exposure seems to increase the incidence of COPD.