title: Risk factors associated with persistent airflow limitation in severe or difficult-to-treat asthma: insights from the TENOR study.
abstract: BACKGROUND
  The Epidemiology and Natural History of Asthma: Outcomes and Treatment Regimens study is among the largest to assess persistent airflow limitation and the first to evaluate a wide range of potential risk factors in high-risk patients with severe or difficult-to-treat asthma. A better understanding is needed regarding factors associated with persistent airway obstruction; this study was performed to determine demographic and clinical characteristics associated with persistent airflow limitation.
  
  
  METHODS
  Data from adult patients (>or= 18 years old) with severe or difficult-to-treat asthma were evaluated. Patients with COPD, obesity with a restrictive respiratory pattern, or a >or= 30 pack-year history of smoking were excluded. Patients with persistent airflow limitation (postbronchodilator FEV1/FVC ratio <or= 70% at two annual consecutive visits) and normal postbronchodilator FEV1/FVC ratio (75 to 85%) were compared. Multivariate analysis identified factors independently associated with persistent airflow limitation.
  
  
  RESULTS
  Of 1,017 patients, 612 patients (60%) showed evidence of persistent airflow limitation. Risk factors were as follows: older age (odds ratio [OR] per 10 years, 1.4; 95% confidence interval [CI], 1.3 to 1.6); male gender (OR, 4.5; 95% CI, 2.3 to 8.5); black ethnicity (OR, 2.2; 95% CI, 1.3 to 3.8); current or past smoking (OR, 3.9; 95% CI, 1.8 to 8.6; and OR, 1.6; 95% CI, 1.2 to 2.3, respectively); aspirin sensitivity (OR, 1.5; 95% CI, 1.0 to 2.4); and longer asthma duration (OR per 10 years, 1.6; 95% CI, 1.4 to 1.8). Protective factors were Hispanic ethnicity, higher education, family history of atopic dermatitis, pet(s) in the home, and dust sensitivity.
  
  
  CONCLUSIONS
  Persistent airflow limitation is prevalent in patients with severe or difficult-to-treat asthma and is associated with identifiable clinical and demographic characteristics.
authors: Genentech, Inc., 1 DNA Way, MS 453B, South San Francisco, CA 94080, USA. lee.june@gene.com
authors: June H
authors: JH
authors: Lee
authors: Tmirah
authors: T
authors: Haselkorn
authors: Larry
authors: L
authors: Borish
authors: Lawrence
authors: L
authors: Rasouliyan
authors: Bradley E
authors: BE
authors: Chipps
authors: Sally E
authors: SE
authors: Wenzel
mesh_terms: D001249:Asthma / Q000503:physiopathology*; D016084:Bronchoconstriction; D016009:Chi-Square Distribution; D018450:Disease Progression; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D013147:Spirometry; D011795:Surveys and Questionnaires; D014797:Vital Capacity