The protective role of country living on skin prick tests, immunoglobulin E and asthma in adults from the Epidemiological study on the Genetics and Environment of Asthma, bronchial hyper-responsiveness and atopy

Background Farming environment and traditional lifestyle seem to protect from childhood allergy. Objective The aim is to analyse the relationships of living in the country to asthma, positive skin prick tests and IgE among adults considering various windows of exposure over the life-span. Methods The study concerns 805 adults drawn from the Epidemiological study on the Genetics and Environment of Asthma, bronchial hyper-responsiveness and atopy (EGEA) (asthmatic cases, non-asthmatic controls, and parents of cases with and without asthma). Ever living in the country concerned 55% of the subjects. Early (beginning <1 years), childhood (beginning ! 16 years), prolonged (duration >= 10 years) and current life in the country were studied. Results The results based on the case control and family components of the study show that IgE levels were significantly lower in those who ever lived in the country and in particular in those who lived for >= 10 years. Positive skin prick tests (SPT) were significantly less prevalent in those who ever lived in the country and in particular in those with childhood ( <= 16 years) exposure. These associations remained independent of age, sex, smoking or asthma with I.-E levels of 64 vs. 88 IU/mL; P = 0.004 for those ever living in the country vs. others and odds ratio for SPT positivity of 0.72 (95% CI [0.53-0.98]). In the more specific group with traditional mode of heating in childhood (use of wood) associations were stronger. The association with asthma, studied in parents of asthmatic probands showed that fathers, but not mothers, of asthmatics were significantly less often asthmatic themselves in relation to country living. Conclusion Country life protects from asthma and adulthood allergy. The protective effect is not restricted to exposure in early childhood.