Central obesity is associated with nonatopic but not atopic asthma in a representative population sample

Background

Epidemiologic studies have consistently demonstrated the association between high body mass index (BMI) and asthma, yet the relationship between asthma and the alternative central obesity phenotypes, waist circumference (WC) and waist-to-hip ratio (WHR), has not been assessed in a representative population sample.
Objective

To determine the strength of the association of WC and WHR with current asthma and whether the association is modified by atopic status in a representative population sample.
Methods

The North West Adelaide Health Study, a biomedical population study of n = 4060, assessed current asthma, respiratory symptoms, and participant demographics by self-completed questionnaire. Clinic assessment included measures of WC and WHR, spirometry, and skin prick tests to a panel of allergens.
Results

Logistic regression analysis showed a significant, marginal increased adjusted risk of asthma associated with obese levels of WC and WHR and BMI ≥35.0 kg/m2 in female subjects only. When the association was considered stratified according to atopic status, the relationship between obese levels of WC and WHR with asthma held only for the nonatopic population in both males (WC: odds ratio [OR] 5.7, 95% confidence interval [CI] 1.1-28.8; WHR: OR 6.2, 95% CI, 1.1-32.9) and females (WC: OR 2.3, 95% CI, 1.2-4.4; WHR: OR 3.0, 95% CI, 1.5-5.9). BMI ≥35.0 kg/m2 showed an inconsistent pattern in the association with asthma.
Conclusion

Central obesity was significantly associated with an increased risk of nonatopic asthma only. The causal pathway is unknown, but this study suggests the involvement of different pathophysiological mechanisms requiring further investigation.
Clinical implications

Asthma should be considered in older, nonatopic, centrally obese, symptomatic individuals.