The relationship between atopy and respiratory symptoms in Alberta farmers

Farming is the commonest occupation in the world and has been associated with several respiratory syndromes. These syndromes include asthma, chronic bronchitis, non-specific airflow limitation, extrinsic allergic alveolitis, organic dust toxic syndrome and mucous membrane irritation syndrome.;Among 781 farmers from two counties in East-Central Alberta, respiratory symptoms were found to occur commonly. Skin atopy to environmental antigens was strongly correlated with asthma and symptoms consistent with asthma, whereas symptoms of chronic bronchitis were not associated with atopy.;When prevalence of respiratory symptoms was compared for 781 farmers and 151 oil workers no difference in frequency of respiratory symptoms were noted when age and smoking history were controlled for. The prevalence of atopy to environmental antigens was significantly lower in farmers than in oil workers. This would suggest that farmers who are atopic select themselves out of the occupation (healthy worker effect).;In non-smoking farmers who reported respiratory symptoms and who had specific and non-specific bronchoprovocation studies performed, the farmers who reported asthma or symptoms consistent with asthma, were more likely to have a positive bronchoprovocation test when compared with farmers reporting chronic bronchitis symptoms. Farmers with atopy to agricultural antigens were more likely to have a positive specific bronchoprovocation test. Correlation between specific and nonspecific bronchoprovocation test were low (OR = 1.66 p = 0.68), suggesting that the most widely used method of identifying those airway reactivity may not be the most sensitive method in this group of workers. Farmers who report symptoms consistent with asthma had responses to the challenge test that were similar to those with asthma and therefore may represent a pool of individuals that may have asthma or occupationally induced asthma.;Certain host factors such as atopy to environmental antigens may predispose an individual to be susceptible to some of these syndromes.