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Original Research: ASTHMA |

Obesity Is a Determinant of Asthma Control Independent of Inflammation and Lung MechanicsObesity Determines Asthma Control

Claude S. Farah, MBBS; Jessica A. Kermode, BSc(Hons1); Sue R. Downie, PhD; Nathan J. Brown, PhD; Kate M. Hardaker, BSc; Norbert Berend, MD, FCCP; Gregory G. King, MBChB, PhD; Cheryl M. Salome, PhD
Author and Funding Information

From the Woolcock Institute of Medical Research (Drs Farah, Downie, Brown, Berend, King, and Salome and Mss Kermode and Hardaker) and the Cooperative Research Centre for Asthma and Airways (Drs Farah, Downie, Brown, Berend, King, and Salome and Mss Kermode and Hardaker), Glebe; the University of Sydney (Drs Farah, Downie, Brown, Berend, King, and Salome and Mss Kermode and Hardaker), Sydney; and the Department of Respiratory Medicine (Dr King), Royal North Shore Hospital, St. Leonards, NSW, Australia.

Correspondence to: Claude S. Farah, MBBS, Airway Physiology Group, The Woolcock Institute of Medical Research, PO Box M77, Missenden Rd, Camperdown, NSW, 2050, Australia; e-mail: cfarah@med.usyd.edu.au


Funding/Support: This study was supported by research grants from the National Health and Medical Research Council of Australia and the Cooperative Research Centre for Asthma and Airways.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestpubs.org/site/misc/reprints.xhtml).


© 2011 American College of Chest Physicians


Chest. 2011;140(3):659-666. doi:10.1378/chest.11-0027
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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/m2) 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 FEV1, Feno, and BMI (model r2 = 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 r2 = 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.

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