title: What is the impact of different spirometric criteria on the prevalence of spirometrically defined COPD and its comorbidities? Results from the population-based KORA study.
abstract: BACKGROUND
  There is an ongoing debate about the appropriate spirometric criterion for airway obstruction to detect COPD. Furthermore, the association of different criteria with comorbidity prevalence and inflammatory biomarkers in advanced age is unclear.
  
  
  METHODS
  Spirometry was performed in a population-based study (n=2,256) covering an age range of 41-90 years. COPD was spirometrically determined either by a fixed ratio (FR) of <0.7 for forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) or by FEV1/FVC below the lower limit of normal (LLN). Comorbidity prevalences and circulating biomarker levels (C-reactive protein [CRP], interleukin [IL]-6) were compared between subjects with or without COPD by the two criteria using logistic and multiple regression models, adjusting for sex and age.
  
  
  RESULTS
  The prevalence of spirometrically defined COPD by FR increased with age from 10% in subjects aged <65 years to 26% in subjects aged ≥75 years. For LLN-defined COPD, it remained below 10% for all age groups. Overall, COPD diagnosis was not associated with specific comorbidities, except for a lower prevalence of obesity in both FR- and LLN-defined cases. Both CRP and IL-6 tended to be higher in cases by both criteria.
  
  
  CONCLUSIONS
  In a population-based cohort of adults up to the age of 90 years, the prevalence of spirometrically defined COPD was higher for the FR criterion than for the LLN criterion. This difference increased with age. Neither prevalences of common comorbidities nor levels of the biomarkers, CRP or IL-6, were conclusively associated with the selection of the COPD criterion. Results have to be considered in light of the predominantly mild cases of airway obstruction in the examined study population.
authors: Institute of Epidemiology I, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg; Institute and Outpatient Clinic for Occupational, Social and Environmental Medicine, Ludwig-Maximilians-Universität; Institute of General Practice, University Hospital Klinikum rechts der Isar, Technische Universität München, Munich.
authors: Stefan
authors: S
authors: Karrasch
authors: Institute of Epidemiology I, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg.
authors: Irene
authors: I
authors: Brüske
authors: Institute of Epidemiology I, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg.
authors: Maia P
authors: MP
authors: Smith
authors: Institute of Epidemiology II, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg.
authors: Barbara
authors: B
authors: Thorand
authors: Institute of Epidemiology II, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg; German Center for Diabetes Research (DZD), Munich/Neuherberg, Germany.
authors: Cornelia
authors: C
authors: Huth
authors: Institute of Epidemiology II, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg.
authors: Karl-Heinz
authors: KH
authors: Ladwig
authors: Division of Genetic Epidemiology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Medical University of Innsbruck, Innsbruck, Austria.
authors: Florian
authors: F
authors: Kronenberg
authors: Institute of Epidemiology I, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg; Comprehensive Pneumology Center Munich (CPC-M), Member of the German Center for Lung Research.
authors: Joachim
authors: J
authors: Heinrich
authors: Institute of Health Economics and Health Care Management, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.
authors: Rolf
authors: R
authors: Holle
authors: Institute of Epidemiology II, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg.
authors: Annette
authors: A
authors: Peters
authors: Institute of Epidemiology I, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg; Comprehensive Pneumology Center Munich (CPC-M), Member of the German Center for Lung Research.
authors: Holger
authors: H
authors: Schulz
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000032:analysis; D015897:Comorbidity; D005260:Female; D005541:Forced Expiratory Volume; D005858:Germany / Q000453:epidemiology; D006801:Humans; D015850:Interleukin-6 / Q000097:blood; D016014:Linear Models; D016015:Logistic Models; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011237:Predictive Value of Tests; D015995:Prevalence; D011379:Prognosis; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology* / Q000503:physiopathology; D012307:Risk Factors; D013147:Spirometry; D014797:Vital Capacity
chemical_list: D015415:Biomarkers; C508600:IL6 protein, human; D015850:Interleukin-6; D002097:C-Reactive Protein
keywords: biomarkers; chronic obstructive pulmonary disease; comorbidity; prevalence; spirometry