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

Abstract

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 FEV1/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 FEV1 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 FEV1% 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.

Figure 1.

Post-bronchodilator (BD) FEV₁ and FEV₁/FVC ratio by year. The figure shows the post-BD FEV₁ (% predicted) and FEV₁/FVC ratio at baseline (B) and each follow-up year (men, solid diamonds; women, open circles; FEV₁, solid lines; FEV₁/FVC ratio, dashed lines).

Figure 2.

Smoking category at baseline and each follow-up year. The figure shows the proportion of subjects in each smoking intensity category at baseline (B) and each follow-up year. The lower segment of each bar (no fill) represents the % of nonsmokers (solid black segment). The segments above sequentially represent smoking category by cigarettes/day: 1–15 (horizontal bars); 16–25 (dots); 26–35 (vertical bars); 36–45 (dense horizontal bars); 46 or more (solid black).