FEV₁ decline in occupational asthma

Abstract

Background: In occupational asthma continued workplace exposure to the causative agent is associated with a poor prognosis. However, there is little information available on how rapidly lung function declines in those who continue to be exposed, nor how removal from exposure affects lung function.

Methods: Forced expiratory volume in 1 second (FEV₁) was studied in 156 consecutive subjects with occupational asthma (87% due to low molecular weight agents) using simple regression analyses to provide estimates of the decline in FEV₁ before and after removal from exposure.

Results: In 90 subjects in whom FEV₁ measurements had been performed for at least 1 year before removal from exposure (median 2.9 years), the mean (SE) rate of decline in FEV₁ was 100.9 (17.7) ml/year. One year after removal from exposure FEV₁ had improved by a mean (SE) of 12.3 (31.6) ml. The mean (SE) decline in FEV₁ was 26.6 (18.0) ml/year in 86 subjects in whom measurements were made for at least 1 year (median 2.6 years) following removal from exposure. The decline in FEV₁ was not significantly worse in current smokers than in never smokers, nor was it affected by the use of inhaled corticosteroids.

Conclusion: FEV₁ declines rapidly in exposed workers with occupational asthma. Following removal from exposure, FEV₁ continued to decline but at a slower rate, similar to the rate of decline in healthy adults.