Setting: Two-phased study of a general population sample in Norway.
Objective: To assess the prevalence of work-related asthma by sex, age and smoking habits.
Design: The first phase, a mail questionnaire on asthma to a random sample of the general population of Hordaland County, Norway, gave a 90% response. A stratified sample of the responders (n = 1512) was invited to complete an occupational history questionnaire and performing spirometry and bronchial hyperresponsiveness. The attendance rate was 84%. Asthmatics were defined as having work-related asthma if they answered positively the questions: "Have you ever had respiratory symptoms in relation to your work? Did the symptoms improve on absence from work?"
Results: The prevalence of work-related asthma was 0.9% in this population, constituting 28% of all asthmatics (95% confidence interval 25-31). The prevalence of work-related asthma was twice as high in men as in women, and did not differ significantly with age or between smoking groups.
Conclusion: Work-related asthma amounts to a significant proportion of total asthma in this population. This should be taken into account by health planners as it is by definition a preventable disorder.