Prevalence and risk factors for COPD in greenhouse farmers: a large, cross-sectional survey of 5,880 farmers from northeast China

BACKGROUND COPD is one of the most common chronic diseases, and more and more farmers who were frequently exposed to greenhouse environments were diagnosed with COPD. However, little information is available on the prevalence of COPD among the greenhouse farmers. This study was conducted to assess the prevalence of COPD and investigate the potential risk factors for COPD among the Chinese greenhouse farmers. METHODS Cross-sectional studies involving a sample of greenhouse farmers living in northeast China were performed via stratified-cluster-random sampling. All subjects were interviewed using a uniform questionnaire and underwent pulmonary function tests between 2006 and 2009, based on the diagnostic criteria of the Global Initiative for Chronic Obstructive Lung Disease. Multiple logistic regression analysis was conducted to examine the risk factors for COPD. RESULTS Of the 5,880 greenhouse farmers from northeast China who were originally selected for this study, 5,420 questionnaires were completed. The overall prevalence of COPD in greenhouse farmers was 17.5%. The COPD prevalence was significantly higher in elderly subjects (≥50 years), current smokers, in those with lower body mass index (≤18.5 kg/m(2)) and less education, in those who were exposed to mushroom, flowers and poultry, and in those living in mountain and coastal region. Multiple logistic regression analysis revealed that age over 50 years old (odds ratio [OR]=298.69, 95% confidence interval [CI]=121.57-733.84), smoking (OR=2.18, 95% CI=1.84-2.59), planting mushroom and flowers (OR=1.46 and 1.53, 95% CI=1.13-1.87 and 1.24-1.95), and living in mountain and coastal region (OR=1.68 and 1.35, 95% CI=1.37-2.06 and 1.10-1.65) were associated with the development of COPD among greenhouse farmers. CONCLUSION In northeast China, COPD is highly prevalent among greenhouse farmers, and advanced age, smoking, planting mushroom, and flowers, as well as living in mountain and coastal regions, are potential risk factors for this disease.