Obesity is a determinant of asthma control independent of inflammation and lung mechanics

Authors

Claude Farah, Woolcock Institute of Medical Research, Cooperative Research Centre for Asthma and Airways, University of Sydney
Jessica Kermode, Cooperative Research Centre for Asthma and Airways, Woolcock Institute of Medical Research, University of Sydney
Susan R. Downie, University of Wollongong, Woolcock Institute of Medical Research, University of SydneyFollow
Nathan P. Brown, Woolcock Institute of Medical Research, Cooperative Research Centre for Asthma and Airways, University of SydneyFollow
Kate Hardaker, Cooperative Research Centre for Asthma and Airways, Woolcock Institute of Medical Research, University of Sydney
Norbert Berend, Cooperative Research Centre for Asthma and Airways, Woolcock Institute of Medical Research, University of Sydney
Gregory King, Cooperative Research Centre for Asthma and Airways, Woolcock Institute of Medical Research, University of Sydney
Cheryl Salome, Cooperative Research Centre for Asthma and Airways, Woolcock Institute of Medical Research, University of Sydney

RIS ID

116473

Publication Details

Farah, C. S., Kermode, J. A., Downie, S. R., Brown, N. J., Hardaker, K. M., Berend, N., King, G. G. & Salome, C. M. (2011). Obesity is a determinant of asthma control independent of inflammation and lung mechanics. Chest, 140 (3), 659-666.

Abstract

Background: It is unclear why obesity is associated with worse asthma control. We hypothesized that(1) obesity affects asthma control independent of spirometry, airway inflammation, and airway hyperresponsiveness (AHR) and (2) residual symptoms after resolution of inflammation are due to obesity-related changes in lung mechanics. Methods: Forty-nine subjects with asthma underwent the following tests, before and after 3 months of high-dose inhaled corticosteroid (ICS) treatment: five-item asthma control questionnaire (ACQ-5), spirometry, fraction of exhaled nitric oxide (FENO), methacholine challenge, and the forced oscillation technique, which allows for the calculation of respiratory system resistance (Rrs) and respiratory system reactance (Xrs) as indicators of airway caliber and elastic load, respectively. The effects of treatment were assessed by BMI group (18.5-24.9, 25-29.9, and ≥30 kg/m 2 ) using analysis of variance. Multiple regression analyses determined the independent predictors of ACQ-5 results. Results: At baseline, the independent predictors of ACQ-5 results were FEV 1 , F ENO, and BMI (model r 2 = 0.38, P < .001). After treatment, asthma control, spirometry, airway inflammation, and AHR improved similarly across BMI groups. The independent predictors of ACQ-5 results after treatment were Rrs and BMI(model r 2 = 0.42, P,.001). Conclusions: BMI is a determinant of asthma control independent of airway inflammation, lung function, and AHR. After ICS treatment, BMI again predicts ACQ-5 results, but independent of obesity-related changes in lung mechanics. 2011 American College of Chest Physicians.