Effect of occupational exposures on decline of lung function in early chronic obstructive pulmonary disease

Rationale: Several occupational exposures adversely affect lung function. Objectives: This study reports the influence of continued occupational dust and fume exposures on the rate of decline of lung function in participants with early chronic obstructive pulmonary disease (COPD) studied in a population-based study. Methods: Subjects consisted of 5,724 participants in the Lung Health Study, a multicenter study of smoking cessation and anticholinergic bronchodilator administration in smokers with early COPD (3,592 men; 2,132 women). Average post-bronchodilator FEV₁ at entry was 78.4% predicted for men and 78.2% predicted for women; all participants had an FEV ₁/FVC ratio less than 0.70. Measurements and Main Results: Participants underwent a baseline evaluation and five annual follow-up assessments, including questionnaires and spirometry. The effect of ongoing dust or fume exposure on FEV₁ in each follow-up year was statistically evaluated with a mixed-effects regression model, which was adjusted for FEV ₁ at entry, age, airway responsiveness to methacholine, baseline smoking intensity, and time-varying (yearly) smoking status during each follow-up year. In men with early COPD, each year of continued fume exposure was associated with a 0.25% predicted reduction in post-bronchodilator FEV ₁% predicted. Continued smoking and airway hyperresponsiveness were also associated with reduction in FEV₁ during each year of follow-up in both men and women. Statistically significant effects of dust exposure on the rate of decline were not found, nor were effects of fume exposure noted in women. Conclusions: These results suggest a need for secondary prevention by controlling occupational fume exposures.