Relation of bronchial responsiveness to body mass index in the ECRHS

Background: There is substantial evidence for an association between symptoms of asthma and overweight or obesity. However, a study that reported no association between bronchial responsiveness (BHR) and body mass index (BMI) suggested that the relation of symptoms to obesity was due to increased diagnosis of asthma. The relation of BHR to BMI was therefore investigated in a large multi-centre study. Methods: Data were obtained for 11 277 participants in stage II of the European Community Respiratory Health Survey (ECRHS). BHR to methacholine was analysed in relation to BMI adjusted for a number of factors known to be associated with BHR, including baseline lung function and allergen sensitisation, and combined across 34 centres using random effects meta-analysis. Results: BHR increased with increasing BMI in men (ECRHS slope changed by -0.027 for each unit increase in BMI, 95% confidence interval -0.044 to -0.0 10, p=0.002), but the relation in women was weak (-0.0 14, 95% CI -0.033 to 0.005, p=0.14). There was no evidence for an interaction of sex with BMI (p=0.41). Conclusions: BHR is related to BMI in the ECRHS. This suggests that the association is not due to greater diagnosis or perception of symptoms in obese people compared with those of normal weight. The data do not support the finding by some studies of a relation between asthma and obesity in women but not in men.