Occupational Asthma Reference
Anees W, Moore VC, Burge PS,
FEV1 decline in occupational asthma,
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: We studied FEV1 in 156 consecutive subjects with occupational asthma (87% due to low molecular weight agents) using simple regression analyses to provide estimates of FEV1 decline before and after removal from exposure.
Results: In 90 subjects who had FEV1 measurements made over at least a year prior to removal (median 2.9 years), mean rate of FEV1 decline was 100.9 ml per year (standard error 17.7). One year after removal from exposure, FEV1 had improved by 12.3 ml (standard error 31.6). FEV1 declined at an average of 26.6 ml per year (standard error 18ml) in 86 subjects who had measurements over at least one year (median 2.6 years) following removal from exposure. FEV1 decline was not significantly worse in current versus never smokers, nor was it affected by 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.
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FEV1 decline is accelerated after sensitisation even with inhaled corticosteroids and reduction of exposure. After complete removal there is initial improvement in FEV1 (which is relatively small), before FEV1 decline returns to normal levels. The evidence relates to a mixture of low molecular weight agents.
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