The Effect of Childhood Farm Exposure on Adult Respiratory Symptoms and Proinflammatory Cytokine Responsiveness in Agricultural Workers

Introduction: Studies have shown that the farm exposes workers and family members to countless microorganisms such as, gram-negative bacteria that possess endotoxins, which have been demonstrated to contribute to lung disease, such as asthma, in exposed workers. Results of studies of children show conflicting results regarding the development of asthma or asthma-like symptoms in response to farm exposures. European children show a “protective effect” against atopy and asthma during adolescence, while North American children show a higher prevalence of asthma or asthma-like symptoms. Also, whether this protective effect carries into adulthood is unclear. Some studies show a low prevalence of asthma or asthma-like symptoms in adults with childhood farm exposures, and some studies show a high prevalence of asthma or asthma-like symptoms in adulthood. Aim: 1) Determine if childhood farm exposure has a protective effect on the prevalence of respiratory symptoms in a population of adult agricultural workers, and 2) Determine whether in vitro proinflammatory responsiveness to organic dust extract is decreased among adults with childhood farm exposure compared to those without early childhood farm exposure. Method: The study population for this analysis was 681 adult U.S. Veterans that worked on a farm as an adult for more than two years. Chi-square and logistic regression were done to determine an association between chronic respiratory symptoms and early childhood farm exposure. A whole blood assay was used to measure responsiveness to organic dust extract. Interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) were measured by ELISA at baseline, ODE-stimulated, and as the difference between baseline and ODE-stimulated levels. Linear regression and student’s t-test examined the association of cytokine levels and early childhood farm exposure. Results: There was no significant associations between childhood farm exposure and chronic respiratory symptoms. The odds of chronic respiratory symptoms were similar between those with or without early childhood farm exposure. Also, early childhood exposures were not a predictor for cytokine responsiveness. Conclusion: These results conclude the need for more analysis to be done regarding childhood exposure and the development of adult chronic respiratory symptoms, especially within the veteran farming population. Future analysis should include the consumption of unpasteurized milk, age of exposure, alcohol use amongst veterans, and the type and location of farming practices that exist within the United States