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/m²) 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.

Key words: Leptin, hygiene hypothesis, inhalant allergens, specific IgE

Abbreviations used: BMI, Body mass index, CI, Confidence interval, ETS, Environmental tobacco smoke, OR, Odds ratio