Prevalence and risk factors for COPD in farmers: a cross-sectional controlled study

There are conflicting data regarding the magnitude and determinants of chronic obstructive pulmonary disease (COPD) risk in farmers. In a cross-sectional study of 917 nonfarming working controls and 3787 farmers aged 40-75 years, we assessed respiratory symptoms, tobacco exposure, job history (without direct exposure measurement) and lung function. COPD was defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) criterion (post-bronchodilator forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) <0.70) and by the Quanjer reference equation (post-bronchodilator FEV1/FVC <lower limit of normal (LLN)). The prevalence (95% CI) of COPD according to the GOLD criterion was 5.1% (4.4-5.8%) and 2.9% (1.8-4.0%) in farmers and controls, respectively (p=0.005), and 3.1% (2.5-3.6%) and 1.5% (0.7-2.3%), respectively, for the LLN criterion (p<0.01). For both COPD criteria after adjustment for age, sex and smoking status, COPD prevalence was similar in controls and crop farmers. Compared to controls, four job categories had a higher prevalence of COPD according to the GOLD criterion, namely, cattle breeders, swine breeders, poultry breeders and breeders of two or more livestock types. Among cattle breeders, only those from Franche-Comte had higher prevalence of COPD according to both GOLD and LLN criteria. The prevalence of COPD in farmers is higher than in nonfarming working controls, and depends on the farming activity, the region and the criterion used to define COPD.