Relation between respiratory symptoms, type of farming, and lung function disorders in farmers.

Respiratory symptoms and function were examined in a random sample of 181 farmers (124 pig farmers and 57 dairy farmers) with a mean age of 43 years. Wheezing and shortness of breath during work in the animal house were significantly associated with pig farming (odds ratio 11.4), current smoking (odds ratio 2.2), bronchial hyperreactivity (odds ratio 3.8), and low FEV1 (odds ratio 3.4). Pig farmers had a slightly lower FEV1 than dairy farmers (101% versus 104% predicted, NS). Symptomatic farmers had significantly lower FEV1 than symptomless farmers (93% versus 106% predicted). A multiple linear regression analysis of the cross sectional values of FEV1 showed that there was a decline in FEV1 associated with pig farming (-12 ml/year of pig farming) and smoking (-23 ml/pack year) in addition to the age related decline of 32 ml/year. A multiple linear regression analysis of PC20 histamine showed that bronchial reactivity increased with age, number of pack years, and number of years in pig farming. Work in closed pig rearing units is a pulmonary health hazard and causes decline in lung function.