Respiratory symptoms in Swiss farmers: an epidemiological study of risk factors

BACKGROUND: The study was undertaken to assess the prevalence and risk factors of self-reported asthma, symptoms of chronic bronchitis, hay fever, and work-related respiratory symptoms in Swiss farmers as well as to compare the prevalence rates of respiratory symptoms with the Swiss population (SAPALDIA-Study). METHODS: An epidemiological study was performed with a representative sample of 1,542 Swiss farmers using a self-administered questionnaire. To investigate the effect of the type of farming on reported symptoms, the farmers were subdivided into seven groups according to the time farmers spent in different animal confinement buildings. A multivariate analysis was performed by the methods of binary and multivariate logistic regression adjusted for age and smoking habits. RESULTS: In farmers the prevalence rate was 16.0% for chronic bronchitis, 15.4% for asthma symptoms, and 42.0% for reporting at least one work-related symptom. Using logistic regression analysis, it was established that poultry farming and pig/cattle farming was a risk factor for reporting nasal irritation at work [OR 5.33, (1.57-18.0), OR 3.37 (1.04-10.87)]. Poultry farmers experienced the highest symptom rates. In crop farmers, the prevalence for chronic bronchitis was increased [OR 2.32 (1.03-5.23)]. Over 4 hr spent per day in animal confinement buildings more than doubled the risk for reporting chronic bronchitis [OR 2.61 (1.01-6.76)] and phlegm [OR 2.3 (0.99-5.4)] independent of the type of farming. The comparison of Swiss farmers with the Swiss population showed a twofold elevated risk of reporting chronic bronchitis [OR 1.89 (1.32-2.95)] and a 4.5-fold elevated risk for bringing up phlegm regularly [OR 4.5 (3.25-6.69)] in farmers. In contrast, the risk of farmers to report nasal allergies was less than half as high [OR 0.40 (0.29-0.56)] as that of the general population. CONCLUSIONS: This study shows that agricultural work in Switzerland is associated with an elevated risk for reporting symptoms of chronic bronchitis and chronic phlegm compared with the general Swiss population. These main results most likely indicate occupational disorders as the exposure-response relationship (hours spent in animal confinements) was particularly obvious for these symptoms.