title: Comparison of spatially matched airways reveals thinner airway walls in COPD. The Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study and the Subpopulations and Intermediate Outcomes in COPD Study (SPIROMICS).
abstract: BACKGROUND
  COPD is characterised by reduced airway lumen dimensions and fewer peripheral airways. Most studies of airway properties sample airways based upon lumen dimension or at random, which may bias comparisons given reduced airway lumen dimensions and number in COPD. We sought to compare central airway wall dimensions on CT in COPD and controls using spatially matched airways, thereby avoiding selection bias of airways in the lung.
  
  
  METHODS
  The Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study and Subpopulations and Intermediate Outcomes in COPD Study (SPIROMICS) recruited smokers with COPD and controls aged 50-79 years and 40-80 years, respectively. COPD was defined by current guidelines. Using CT image data, airway dimensions were measured for all central airway segments (generations 0-6) following 5 standardised paths into the lungs. Case-control airway comparisons were spatially matched by generation and adjusted for demographics, body size, smoking, CT dose, per cent emphysema, airway length and lung volume.
  
  
  RESULTS
  Among 311 MESA COPD participants, airway wall areas at generations 3-6 were smaller in COPD compared with controls (all p<0.001). Among 1248 SPIROMICS participants, airway wall areas at generations 1-6 were smaller (all p<0.001), and this reduction was monotonic with increasing COPD severity (p<0.001). In both studies, sampling airways by lumen diameter or randomly resulted in a comparison of more proximal airways in COPD to more peripheral airways in controls (p<0.001) resulting in the appearance of thicker walls in COPD (p<0.02).
  
  
  CONCLUSIONS
  Airway walls are thinner in COPD when comparing spatially matched central airways. Other approaches to airway sampling result in comparisons of more proximal to more distal airways and potentially biased assessment of airway properties in COPD.
authors.affiliation: Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, New York, USA Department of Medicine, McGill University, Montreal, Canada.
authors.forename: Benjamin M
authors.initials: BM
authors.lastname: Smith
authors.affiliation: Departments of Radiology, Medicine and Biomedical Engineering, University of Iowa, Iowa City, Iowa, USA.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Hoffman
authors.affiliation: Department of Statistics, Columbia University, New York, New York, USA.
authors.forename: Dan
authors.initials: D
authors.lastname: Rabinowitz
authors.affiliation: Department of Medicine, Wake Forest University, Winston-Salem, North Carolina, USA.
authors.forename: Eugene
authors.initials: E
authors.lastname: Bleecker
authors.affiliation: Department of Medicine, University of California San Francisco, San Francisco, California, USA.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Christenson
authors.affiliation: Deparment of Biostatistics, University of North Carolina Chapel Hill, Chapel Hill, North Carolina, USA.
authors.forename: David
authors.identifier: http://orcid.org/0000-0002-4313-9235
authors.initials: D
authors.lastname: Couper
authors.affiliation: Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, New York, USA.
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Donohue
authors.affiliation: Department of Medicine, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Meilan K
authors.initials: MK
authors.lastname: Han
authors.affiliation: Department of Medicine, Johns Hopkins University, Baltimore, Maryland, USA.
authors.forename: Nadia N
authors.initials: NN
authors.lastname: Hansel
authors.affiliation: Department of Medicine, University of Utah, Salt Lake City, Utah, USA.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Kanner
authors.affiliation: Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Kleerup
authors.affiliation: Department of Medicine, University of Nebraska Medical Center, Omaha, Nebraska, USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Rennard
authors.affiliation: Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, New York, USA Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York, USA.
authors.forename: R Graham
authors.initials: RG
authors.lastname: Barr
mesh_terms: D000368:Aged; D050197:Atherosclerosis / Q000150:complications / Q000208:ethnology*; D005006:Ethnicity; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000208:ethnology / Q000503:physiopathology*; D012137:Respiratory System / Q000000981:diagnostic imaging*; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed; D014481:United States / Q000453:epidemiology
keywords: COPD epidemiology; Imaging/CT MRI etc