title: Fixed airflow obstruction among nonsmokers with asthma:a case-comparison study.
abstract: BACKGROUND
  Airflow obstruction in asthma is usually reversible, but fixed obstruction develops in some individuals. Little is known about risk factors for development of fixed airflow obstruction in nonsmokers with asthma.
  
  
  METHODS
  This case-comparison study recruited nonsmokers aged over 45 years with physician-diagnosed asthma from specialist outpatient clinics and primary care. Two age-matched groups were recruited on the basis of spirometry: anobstructed group (post-bronchodilator FEV(1) ≤ 70% predicted, FEV1/FVC ratio < lower limit of normal) and a control group with normal lung function. Subjects completed a questionnaire and interview, and underwent spirometry, venesection, exhaled nitric oxide (ENO) measurement, allergen skinprick testing, and formal lung function testing.
  
  
  RESULTS
  Thirty-four obstructed subjects and 40 controls participated in the study. Obstructed subjects exhibited greater evidence of systemic inflammation, abnormal glucose homeostasis, and central obesity than controls. Obstructed subjects reported longer duration of asthma, and childhood respiratory infection was commoner in that group. Metabolic syndrome prevalence was similar between groups, but several features of insulin resistance were associated with reduced FEV(1). Cough and sputum were common among controls.
  
  
  CONCLUSIONS
  Risk of fixed airflow obstruction may correlate with lifetime asthma duration. Individuals with coexisting asthma and fixed airflow obstruction have heightened systemic inflammation. A variety of chronic respiratory symptoms are common among "healthy" nonsmokers with asthma.
authors.affiliation: Department of Medicine, University of Auckland, Auckland, New Zealand. p.sexton@auckland.ac.nz
authors.forename: Paul
authors.initials: P
authors.lastname: Sexton
authors.forename: Peter
authors.initials: P
authors.lastname: Black
authors.forename: Lian
authors.initials: L
authors.lastname: Wu
authors.forename: Fay
authors.initials: F
authors.lastname: Sommerville
authors.forename: Maye
authors.initials: M
authors.lastname: Hamed
authors.forename: Patricia
authors.initials: P
authors.lastname: Metcalf
authors.forename: John
authors.initials: J
authors.lastname: Kolbe
mesh_terms: D000402:Airway Obstruction / Q000453:epidemiology* / Q000378:metabolism / Q000503:physiopathology; D001249:Asthma / Q000453:epidemiology* / Q000378:metabolism / Q000503:physiopathology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007249:Inflammation / Q000453:epidemiology; D008297:Male; D024821:Metabolic Syndrome / Q000453:epidemiology; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism; D009765:Obesity / Q000453:epidemiology; D012141:Respiratory Tract Infections / Q000453:epidemiology; D013147:Spirometry; D014028:Tobacco Smoke Pollution
chemical_list: D014028:Tobacco Smoke Pollution; D009569:Nitric Oxide