Consequences of occupational asthma

Patients, methods, and results

We surveyed all patients referred to a specialist clinic between 1987 and 1992 who had been given a final diagnosis of asthma. All had been referred for investigation of a possible occupational cause; most had subsequently been discharged. Using the clinician's final diagnosis, patients were divided into three categories: those with occupationally induced asthma, those with pre-existing or coexisting asthma exacerbated by work, and those with asthma unrelated to work. Diagnoses were made by a combination of clinical history, measurement of specific antibodies, serial peak flow recordings, and specific inhalation testing. A postal questionnaire inquired into job changes made because of asthma, consequences on income, difficulties in acquiring new work, and current treatment. Socioeconomic group was recorded by using a standard classification.4

We surveyed 225 subjects: 113 (50%) had occupational asthma, 37 (16%) had asthma exacerbated by work, and 75 (33%) has asthma unrelated to work. These proportions did not change over the five years, allowing a similar length of follow up for each category. The response rate was 89% after exclusion of 24 who did not receive a questionnaire. Responders did not differ significantly from non-responders in age, sex, diagnosis, or socioeconomic group.

The mean age in each category was about 40 years. Thirty one per cent of those with occupational asthma were women (35); 33% (37) were in socioeconomic groups I and II, accounted for by the high proportion of research scientists and technicians. The other categories had twice as many men as women and had higher proportions in lower socioeconomic groups.

The effects on income and employment were similar in patients with occupational and work exacerbated asthma but differed significantly in patients with asthma unrelated to work (table). Proportions of those currently employed were similar in all categories, but those with occupational and work exacerbated asthma reported greater difficulty in finding new work and higher proportions had changed or suffered disruption to their jobs. There were no consistent differences between men and women. Those in manual socioeconomic groups reported greater difficulty in finding new work, greater loss of income, and were less likely to be currently employed.

Earnings were adversely affected in all categories, more in those with occupational or work exacerbated asthma, of whom 30% reported losing more than 40% of income (χ²=7.43, df=1, P=0.006) compared with those whose asthma was unrelated to work. This loss was not offset by industrial injuries disablement benefit, which was more commonly received by patients referred before 1990.

Comment

In addition to the respiratory disability caused by asthma, patients with work related asthma, whether initiated or provoked by agents inhaled at work, suffer adverse economic and employment consequences. For most outcomes there was little difference between those with occupational or work exacerbated asthma. For many patients, continuing a chosen career, often after many years' training, was not possible. Those in higher socioeconomic groups found it easier to diversify into related careers; skilled manual workers had less opportunity to transfer into equally skilled work and often obtained unskilled work or became unemployed. Those with work related asthma who had made no change (10%) may have decided that their livelihood was as important as their health. The low proportion receiving disablement benefit has been a consistent finding in similar studies. Some patients did not claim benefit because they believed it would stigmatise them in the job market. Patients clearly need appropriate advice about their entitlements.

These findings highlight the importance of correctly identifying any relation between asthma and work and also the dangers of false attribution.