title: Obesity is a determinant of asthma control independent of inflammation and lung mechanics.
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/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 FEV(1), 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.
authors.affiliation: Woolcock Institute of Medical Research, Glebe, Australia; Cooperative Research Centre for Asthma and Airways, Glebe, Australia; University of Sydney, Sydney, Australia. Electronic address: cfarah@med.usyd.edu.au.
authors.forename: Claude S
authors.initials: CS
authors.lastname: Farah
authors.affiliation: Woolcock Institute of Medical Research, Glebe, Australia; Cooperative Research Centre for Asthma and Airways, Glebe, Australia; University of Sydney, Sydney, Australia.
authors.forename: Jessica A
authors.initials: JA
authors.lastname: Kermode
authors.affiliation: Woolcock Institute of Medical Research, Glebe, Australia; Cooperative Research Centre for Asthma and Airways, Glebe, Australia; University of Sydney, Sydney, Australia.
authors.forename: Sue R
authors.initials: SR
authors.lastname: Downie
authors.affiliation: Woolcock Institute of Medical Research, Glebe, Australia; Cooperative Research Centre for Asthma and Airways, Glebe, Australia; University of Sydney, Sydney, Australia.
authors.forename: Nathan J
authors.initials: NJ
authors.lastname: Brown
authors.affiliation: Woolcock Institute of Medical Research, Glebe, Australia; Cooperative Research Centre for Asthma and Airways, Glebe, Australia; University of Sydney, Sydney, Australia.
authors.forename: Kate M
authors.initials: KM
authors.lastname: Hardaker
authors.affiliation: Woolcock Institute of Medical Research, Glebe, Australia; Cooperative Research Centre for Asthma and Airways, Glebe, Australia; University of Sydney, Sydney, Australia.
authors.forename: Norbert
authors.initials: N
authors.lastname: Berend
authors.affiliation: Woolcock Institute of Medical Research, Glebe, Australia; Cooperative Research Centre for Asthma and Airways, Glebe, Australia; University of Sydney, Sydney, Australia; Department of Respiratory Medicine, Royal North Shore Hospital, St. Leonards, NSW, Australia.
authors.forename: Gregory G
authors.initials: GG
authors.lastname: King
authors.affiliation: Woolcock Institute of Medical Research, Glebe, Australia; Cooperative Research Centre for Asthma and Airways, Glebe, Australia; University of Sydney, Sydney, Australia.
authors.forename: Cheryl M
authors.initials: CM
authors.lastname: Salome
mesh_terms: D000305:Adrenal Cortex Hormones / Q000008:administration & dosage; D000328:Adult; D001249:Asthma / Q000188:drug therapy / Q000453:epidemiology* / Q000503:physiopathology / Q000517:prevention & control*; D015992:Body Mass Index; D016535:Bronchial Hyperreactivity; D001985:Bronchial Provocation Tests; D015897:Comorbidity; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009765:Obesity / Q000453:epidemiology* / Q000503:physiopathology; D010991:Plethysmography; D012129:Respiratory Function Tests; D013147:Spirometry
chemical_list: D000305:Adrenal Cortex Hormones