title: The clinical impact of non-obstructive chronic bronchitis in current and former smokers.
abstract: BACKGROUND
  As the clinical significance of chronic bronchitis among smokers without airflow obstruction is unclear, we sought to determine morbidity associated with this disorder.
  
  
  METHODS
  We examined subjects from the COPDGene study and compared those with FEV1/FVC ≥ 0.70, no diagnosis of asthma and chronic bronchitis as defined as a history of cough and phlegm production for ≥ 3 months/year for ≥ 2 years (NCB) to non-obstructed subjects without chronic bronchitis (CB-). Multivariate analysis was used to determine factors associated with and impact of NCB.
  
  
  RESULTS
  We identified 597 NCB and 4283 CB- subjects. NCB participants were younger (55.4 vs. 57.2 years, p < 0.001) with greater tobacco exposure (42.9 vs. 37.8 pack-years, p < 0.001) and more often current smokers; more frequently reported occupational exposure to fumes (52.8% vs. 42.2%, p < 0.001), dust for ≥ 1 year (55.3% vs. 42.0%, p < 0.001) and were less likely to be currently working. NCB subjects demonstrated worse quality-of-life (SGRQ 35.6 vs. 15.1, p < 0.001) and exercise capacity (walk distance 415 vs. 449 m, p < 0.001) and more frequently reported respiratory "flare-ups" requiring treatment with antibiotics or steroids (0.30 vs. 0.10 annual events/subject, p < 0.001) prior to enrollment and during follow-up (0.34 vs. 0.16 annual events/subject, p < 0.001). In multivariate analysis, current smoking, GERD, sleep apnea and occupational exposures were significantly associated with NCB.
  
  
  CONCLUSIONS
  While longitudinal data will be needed to determine whether NCB progresses to COPD, NCB patients have poorer quality-of-life, exercise capacity and frequent respiratory events. Beyond smoking cessation interventions, further research is warranted to determine the benefit of other therapeutics in this population. Clinical Trials Registration # NCT00608764 (http://clinicaltrials.gov/show/NCT00608764). Link to study protocol: http://www.copdgene.org/sites/default/files/COPDGeneProtocol-5-0_06-19-2009.pdf.
authors.affiliation: Pulmonary & Critical Care Division, University of Michigan Health System, Ann Arbor, MI, USA. Electronic address: carlosma@umich.edu.
authors.forename: Carlos H
authors.initials: CH
authors.lastname: Martinez
authors.affiliation: Division of Pulmonary and Critical Care, Temple University School of Medicine, Philadelphia, PA, USA.
authors.forename: Victor
authors.initials: V
authors.lastname: Kim
authors.affiliation: Respiratory Department, Peking University Third Hospital, Beijing, China.
authors.forename: Yahong
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Radiology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Ella A
authors.initials: EA
authors.lastname: Kazerooni
authors.affiliation: School of Public Health, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Susan
authors.initials: S
authors.lastname: Murray
authors.affiliation: Division of Pulmonary and Critical Care, Temple University School of Medicine, Philadelphia, PA, USA.
authors.forename: Gerard J
authors.initials: GJ
authors.lastname: Criner
authors.affiliation: Pulmonary & Critical Care Division, University of Michigan Health System, Ann Arbor, MI, USA; Medicine Service, VA Healthcare System, Ann Arbor, MI, USA.
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Curtis
authors.affiliation: Department of Medicine, National Jewish Medical and Research Center, Denver, CO, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Regan
authors.affiliation: Channing Division of Network Medicine and Pulmonary and Critical Care Division, Brigham and Women's Hospital, Boston, MA, USA.
authors.forename: Emily
authors.initials: E
authors.lastname: Wan
authors.affiliation: Channing Division of Network Medicine and Pulmonary and Critical Care Division, Brigham and Women's Hospital, Boston, MA, USA.
authors.forename: Craig P
authors.initials: CP
authors.lastname: Hersh
authors.affiliation: Channing Division of Network Medicine and Pulmonary and Critical Care Division, Brigham and Women's Hospital, Boston, MA, USA.
authors.forename: Edwin K
authors.initials: EK
authors.lastname: Silverman
authors.affiliation: Department of Medicine, National Jewish Medical and Research Center, Denver, CO, USA.
authors.forename: James D
authors.initials: JD
authors.lastname: Crapo
authors.affiliation: Pulmonary & Critical Care Division, University of Michigan Health System, Ann Arbor, MI, USA.
authors.forename: Fernando J
authors.initials: FJ
authors.lastname: Martinez
authors.affiliation: Pulmonary & Critical Care Division, University of Michigan Health System, Ann Arbor, MI, USA.
authors.forename: Meilan K
authors.initials: MK
authors.lastname: Han
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D029481:Bronchitis, Chronic / Q000453:epidemiology*; D003371:Cough / Q000453:epidemiology; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009017:Morbidity; D016273:Occupational Exposure / Q000706:statistics & numerical data; D011788:Quality of Life; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology*; D011795:Surveys and Questionnaires
keywords: Cough; GERD; Gastroesophageal reflux; Occupational exposure; Quality of life; Tobacco