Prevalence of chronic bronchitis in farmers according to smoking and atopic skin sensitization.

Development of chronic bronchitis has been shown to depend strongly on smoking habits. Atopy is known to predispose individuals to the development of asthma. Few studies, however, have dealt with the role of the atopic status of the individual as a predisposing factor for chronic bronchitis. In our previous survey among farmers, we observed that chronic bronchitis occurred more often among atopic than non-atopic subjects. Atopy was defined on the basis of past or present atopic manifestations. The association between atopy and chronic bronchitis was re-examined in a separate study of 169 individuals. Using the skin-prick technique we tested these farmers for atopy. The antigen panel included 36 common and farm-related allergens. Among non-smokers with negative skin tests the prevalence of chronic bronchitis was 5.6%, whereas among farmers with positive skin tests (area of at least one skin test reaction equal to 6 mm2 or larger) the prevalence of chronic bronchitis was 15.1%. When age, sex and smoking habits were accounted for statistically, individuals with positive skin tests suffered from chronic bronchitis twice as frequently as subjects with negative skin tests. The predisposing effects of smoking and atopy were of the same order of magnitude. The results of the clinical study of atopy correspond closely to those of the survey study. In the farming population, individuals with an atopic constitution are predisposed to development of chronic bronchitis.