Low prevalence of atopy in young Danish farmers and farming students born and raised on a farm.

Abstract

Background Recent studies have shown that in several countries atopic sensitization to common allergens (common atopy) and atopic symptoms are markedly less prevalent in children living on a farm, compared with non‐farm children living in the same rural areas. Living conditions on farms may, however, vary largely between different countries. It is also not yet known whether the ‘protective’ effect of a farm environment can also be found in adults. Materials and methods Common atopy and respiratory health were assessed by skin prick tests (SPT), questionnaire and measurement of bronchial hyper‐responsiveness (BHR) in the Sund Stald (SUS) study, a cohort study on respiratory health in Danish farming students and conscripts from the same rural areas as controls. Results of SPT were confirmed by IgE serology in all SPT+ subjects and a subset of SPT– subjects. Prevalences of common atopy, respiratory symptoms and bronchial hyper‐ responsiveness were compared for farmers and controls, and for those who had or had not lived on a farm in early childhood. Results In multiple logistic regression analyses adjusting for ever smoking and a familial history of allergy, both being a farmer (ORs 0.62–0.75) and having had a farm childhood (ORs 0.55–0.75) appeared to contribute independently to a lower risk of sensitization to common allergens as assessed by SPT and IgE serology. A farm childhood was also inversely associated with high total IgE (OR 0.68), presence of respiratory symptoms (ORs 0.69–0.79) and BHR (OR 0.61) in these analyses. Direction and strength of the association between being a farmer and respiratory symptoms or BHR varied widely (ORs 0.69–1.28). Conclusion The ‘anti‐atopy’ protective effect of a farm childhood could be confirmed in Danish farming students: prevalences of positive SPT, specific and total IgE, allergic symptoms and BHR were lower in those being born or raised on a farm. Past exposure to the farm environment in early childhood may therefore also contribute to a lower risk of atopic sensitization and disease at a later age.