[High incidence of work-related disease among asthmatics on sick-leave].

Background: We have previously shown that work-related asthma is substantially underreported and usually not notified to the Labour Inspection Authority until it has become chronic and interferes with future work. The aim of this study was to evaluate whether conditions relating to individuals are important for the susceptibility to work-related asthma and to assess whether there is a correspondence between patients' and physicians' perception of the importance of exposure to work in relation to the disease.

Material And Methods: Questionnaires were sent to 824 workers (56% women) aged 18-55 years, who had been on sick leave > 16 days in the years 2000-2003. The disease was classified as work-related asthma if the following questions were answered positively: "Have you ever had respiratory symptoms in relation to your work?" and "Did the symptoms improve on absence from work?"

Results: The response rate was 72%, 58% of the responders were women. 416 (70%) had work-related asthma. There were fewer smokers in the group with work-related asthma than among those without, atopy was equally prevalent. Occupational titles reflected the gender differences of the Norwegian labour force. Indoor climate at the workplace was stated as the most frequent provoking factor. The physicians suspected a relationship to work for about half of the 416, notification was only sent for 21% of the male and 10% of the female employees.

Interpretation: The importance of occupational exposure seems to be underestimated, especially for women with asthma. Neither atopy nor smoking increased the risk for work-related symptoms. Indoors climate at the work place was most often given as the reason for work-related symptoms. A reduction of exposure led to a reduction of symptoms for most individuals.