New-onset COPD and Decline in Lung Function Among Wood Dust-Exposed Workers: Re-analysis of a 6-year Follow-up Study

Objectives: There is a lack of longitudinal studies exploring the association between organic wood dust exposure and new-onset chronic obstructive pulmonary disease (COPD) and change in lung function. We have re-investigated these associations in a 6-year follow-up cohort of furniture workers exposed to wood dust using improved outcome measures and methods. Methods: A large follow-up study of 1112 woodworkers (63%) from the Danish furniture industry and 235 controls (57%) was conducted between 1998 and 2004. Forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), and the ratio (FEV1/FVC) standardized for age, height, and sex using the Global Lung Function Initiative 2012 equations were assessed at baseline and follow-up. Questionnaires on respiratory symptoms, wood dust exposure, and smoking habits were collected. Exposure was assessed as exposure level at baseline and as cumulative exposure in the follow-up period from quantitative task specific job exposure matrix available at both baseline and follow-up based on personal dust sampling using passive dust monitors. The association between exposure to wood dust and new-onset COPD was assessed with logistic regression, whereas the association between wood dust and the longitudinal change in z-score for lung function was assessed with linear regression. Results: Similar associations were seen for different exposure metrics. An exposure-response relation was seen for new-onset COPD for female smokers with an odds ratio (OR) (95% confidence interval [CI]) of 8.47 (0.9-82.4) in the highest exposed group compared to controls, and a significant test for trend P = 0.049. No such association was seen among males for whom only smoking was strongly associated to new-onset COPD. For change in lung function, a significant exposure-response was seen for females, confirming previous findings, with increasing levels of wood dust exposure showing larger decline in lung function (beta [95% CI]: -0.32 Delta zFEV1 (-0.56 to -0.08, P = 0.009) for third quartile exposure compared to controls, test for trend, P = 0.005, equivalent to an excess loss of 125 ml in the 6 years of follow-up). An opposite association was seen for men. Conclusion: In conclusion, we found that female woodworkers have a dose-dependent increased OR of new-onset COPD and an excess decline in lung function suggesting that female woodworkers may be more susceptible to wood dust exposure than male woodworkers. Among male woodworkers, only smoking and asthma were significant predictors for new-onset COPD and excess decline in lung function. These results emphasize that reduction in both smoking and wood dust exposure should continuously be an effort to prevent adverse pulmonary health effects.