Chest
Volume 96, Issue 5, November 1989, Pages 1046-1049
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Clinical Investigations
Occupational Asthma due to Various Agents: Absence of Clinical and Functional Improvement at an Interval of Four or More Years after Cessation of Exposure

https://doi.org/10.1378/chest.96.5.1046Get rights and content

We have previously shown that in some subjects with occupational asthma caused by various agents, there is no improvement approximately two years after exposure ended. These results could be explained by the short interval between diagnosis and follow-up. In the current study, we1 saw 28 subjects with occupational asthma at two intervals, 2.3 years (range, three months to 5.7 years) and 5.8 years (range, 4.3 to 10.9 years) after the cessation of exposure. Various causes of occupational asthma were included. The diagnosis was confirmed in 26 of the cases by specific inhalation challenges in the laboratory, and in the remaining two cases by combined monitoring of peak expiratory flow rates and bronchial responsiveness. All subjects had symptoms of asthma at both follow-up assessments. There were no changes in the need for medication, spirometry, or bronchial hyperresponsiveness. Depending on the interval of the follow-up, four to six subjects required inhaled steroid agents in addition to the usual bronchodilators, 11 had FEV1 less than 80 percent of predicted, and 26 or 27 had an abnormal PC 20 histamine. Only two subjects demonstrated sustained improvement in PC 20 at the first and second follow-ups, and one other showed changes during the second follow-up assessment which were not present at the first. We conclude that except for three subjects, the need for medication did not diminish, nor did airway obstruction and hyperresponsiveness improve in this group of subjects with occupational asthma long after exposure ended. These results differ from other studies, which demonstrated that some recovery takes place in a greater proportion of individuals.

Section snippets

Subjects

In the first follow-up study,4 we surveyed 32 individuals exposed to various agents out of 45 consecutive subjects who satisfied the criteria of follow-up, ie, (1) diagnosis confirmed by specific inhalation challenges in the laboratory or by monitoring of peak expiratory flow rates and bronchial responsiveness (or by both); and (2) cessation of exposure for at least six months. Three subjects were still exposed, one subject sensitized to pollens was contacted during the pollen season and

Results

The mean age of subjects at the time of diagnosis was 46 years (range, 20 to 64 years). The mean durations of exposure before and after the onset of symptoms were 6.3 months (range, 1 to 39 months) and 3.2 months (range, <1 month to 12.5 months), respectively. Follow-up assessments were performed 2.3 years (range, 3 months to 5.7 years) and 5.8 years (range, 4.3 to 10.9 years) after subjects were removed from the workplace.

All subjects were still symptomatic at both follow-ups. Among the group,

Discussion

This study shows that even at a long-term follow-up (>4 years), the symptoms and bronchial hyperresponsiveness of most subjects with occupational asthma persisted. Only a minority of subjects no longer required bronchodilators. Most other studies, summarized in Table 4,1, 2, 3, 4, 5, 6, 7, 8 have also demonstrated a persistence of symptoms and bronchial hyperresponsiveness after subjects left the workplace; however, the percentage of subjects with persisting hyperresponsiveness is generally

ACKNOWLEDGMENTS

We thank Ms. Katherine Tallman for reviewing the manuscript.

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