Adult obesity, farm childhood, and their effect on allergic sensitization

Background: Obesity as well as a reduced microbial exposure, 2 markers of Western lifestyle, might be associated with an increased risk of allergic sensitization. Objective: We aimed to analyze the interplay of these markers of Western lifestyle on allergic sensitization. Methods: A questionnaire survey was completed by rural adults (18-45 years). Clinical assessments included those of sensitization (specific IgE) against inhalant allergens and body mass index (BMI). Subjects were grouped on the basis of their recent BMI (obesity: BMI >= 30 kg/m(2)) and whether they had regular farm contact during the first 3 years of life (farm subjects). Nonobese nonfarm subjects served as the reference group. Overall, 1861 subjects were included in the analyses. Results: Compared with nonobese nonfarm subjects, nonobese farm subjects showed a decreased odds ratio for sensitization (odds ratio, 0.6; 95% CI, 0.5-0.8). This decrease was not observed in obese subjects (obese nonfarm subjects: 1.2, 0.8-1.9; obese farm subjects: 1.0, 0.6-1.6). Associations were similar for symptoms of allergic rhinitis. Conclusion: Obesity, as a risk factor for respiratory allergies per se, might diminish or even cancel the protective effect of a farm childhood. Clinical implications: The high prevalence of respiratory allergies in inner-city societies despite lower levels of hygiene might be explained by obesity.