Mild asthma in overweight women: A new phenotype?

Background: Epidemics of asthma and overweight have been linked recently. They might be associated with systemic inflammation. In asthma hyperresponsiveness to adenosine (AMP) is more closely related to inflammation than to methacholine (MCh). The aim of the study was to determine responsiveness to AMP and MCh in overweight compared with normal weight asthmatics.

Methods: Thirty women were enrolled (19 overweight) with mild controlled asthma according to GINA. A Body Mass Index (BMI) less than 25kg/m(2) was considered as normal and a BMI above 25kg/m(2) as overweight. We assessed the recent control of asthma (ACQ), pulmonary function tests, bronchial responsiveness to MCh and AMP (PC(20) and O'Connor two-point dose-response slope), perception of symptoms (Borg scale), and blood inflammatory markers (leptin and hs-CRP by ELISA).

Results: Overweight had a significant lower dose-response slope of the MCh challenge (p=0.009) as compared to normal weight patients, whereas no significant difference was observed for AMP challenge (p=0.27). Overweight patients had higher intercepts of the Borg scale measured before the MCh and AMP challenge tests (p=0.01 and p=0.03). Plasma leptin (p=0.001) and hs-CRP (p=0.05) concentrations were higher in overweight than normal weight patients. There was no correlation between challenges and inflammatory markers.

Conclusions: Overweight asthmatic women have more pronounced systemic inflammation, but are less responsive to MCh. AMP responsiveness appeared to be comparable between both groups. Our findings suggest that overweight asthmatic women do not feature increased airway inflammation, but do represent a distinct phenotype as compared to normal weight patients.