title: Smoking, longer disease duration and absence of rhinosinusitis are related to fixed airway obstruction in Koreans with severe asthma: findings from the COREA study.
abstract: BACKGROUND
  The clinical manifestations of severe asthma are heterogeneous. Some individuals with severe asthma develop irreversible fixed airway obstruction, which is associated with poor outcomes. We therefore investigated the factors associated with fixed airway obstruction in Korean patients with severe asthma.
  
  
  METHODS
  Severe asthma patients from a Korean adult asthma cohort were divided into two groups according to the results of serial pulmonary function tests. One group had fixed airway obstruction (FAO) [forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) ratio < 0.7, n = 119] and the other had reversible airway obstruction (RAO) [FEV1/FVC ratio ≥ 0.7, n = 116]. Clinical and demographic parameters were compared between the two groups.
  
  
  RESULTS
  Multivariate analysis showed that longer duration of disease, greater amount of cigarette smoking and absence of rhinosinusitis were significantly related to the development of FAO in severe asthmatics. Other parameters, including atopic status, pattern of airway inflammatory cells in induced sputum, and frequency of asthma exacerbations did not differ between the FAO and RAO groups.
  
  
  CONCLUSIONS
  Severe asthma patients with longer disease duration and the absence of rhinosinusitis are more likely to develop FAO. This study also demonstrates the importance of quitting smoking in order to prevent irreversible airway obstruction. Further investigation is required to determine the mechanism by which these factors can modify the disease course in Korean patients with severe asthma.
authors.affiliation: Department of Allergy and Clinical Immunology, Asan Medical Center, University of Ulsan College of Medicine, Asanbyeongwon-gil 86, Songpa-gu, Seoul, 138-736, Korea.
authors.forename: Taehoon
authors.initials: T
authors.lastname: Lee
authors.forename: Yoon Su
authors.initials: YS
authors.lastname: Lee
authors.forename: Yun-Jeong
authors.initials: YJ
authors.lastname: Bae
authors.forename: Tae-Bum
authors.initials: TB
authors.lastname: Kim
authors.forename: Seon Ok
authors.initials: SO
authors.lastname: Kim
authors.forename: Sang-Heon
authors.initials: SH
authors.lastname: Cho
authors.forename: Hee-Bom
authors.initials: HB
authors.lastname: Moon
authors.forename: You Sook
authors.initials: YS
authors.lastname: Cho
mesh_terms: D000328:Adult; D000368:Aged; D000402:Airway Obstruction / Q000188:drug therapy / Q000208:ethnology* / Q000503:physiopathology; D044466:Asian People / Q000706:statistics & numerical data*; D001249:Asthma / Q000188:drug therapy / Q000208:ethnology* / Q000503:physiopathology; D016009:Chi-Square Distribution; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D056910:Republic of Korea / Q000453:epidemiology; D012129:Respiratory Function Tests; D012220:Rhinitis / Q000208:ethnology*; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D012852:Sinusitis / Q000208:ethnology*; D012907:Smoking / Q000208:ethnology*; D013997:Time Factors; D014797:Vital Capacity