title: Majority of never-smokers with airflow limitation do not have asthma: the Copenhagen General Population Study.
abstract: A substantial proportion of individuals with airflow limitation are never-smokers. However, whether never-smokers with airflow limitation have undiagnosed asthma is unknown. We hypothesised that the majority of never-smokers with respiratory symptoms and airflow limitation but without known asthma have undiagnosed asthma by comparing characteristics and prognosis in never-smokers with airflow limitation and asthma (NS+AFL+A) with never-smokers with airflow limitation but without asthma (NS+AFL-A).
  
  
  
  Among 94 079 participants aged 20-100 years from the general population, 39 102 (42%) were never-smokers. In this group, 13 719 (35%) reported to have respiratory symptoms of whom 1610 (12%) had airflow limitation. We investigated characteristics and risk of complications (asthma or COPD exacerbations, pneumonias and all-cause mortality) and comorbidities (lung cancer, ischaemic heart disease, myocardial infarction, deep venous thrombosis and PE) during 4.5 years median follow-up.
  
  
  
  NS+AFL-A compared with NS+AFL+A reported less allergy and respiratory symptoms, and had higher FEV1 and lower levels of eosinophils and IgE in peripheral blood. NS+AFL+A had increased risk of asthma and COPD exacerbations, but not of pneumonias; adjusted HRs in NS+AFL+A compared with NS+AFL-A were 16 (95% CI 3.7 to 73) for asthma exacerbations and 15 (2.8 to 80) for COPD exacerbations. Still, NS+AFL-A had increased risk of COPD exacerbations and pneumonias, but not of asthma exacerbations; adjusted HRs in NS+AFL-A compared with never-smokers without airflow limitation or asthma (NS-AFL-A) were 7.7 (2.8 to 21) for COPD exacerbations and 1.7 (1.3 to 2.3) for pneumonias. Risk of comorbidities or all-cause mortality was not increased in NS+AFL-A or NS+AFL+A compared with NS-AFL-A.
  
  
  
  Majority of NS+AFL-A do not seem to have undiagnosed asthma and may instead have airflow limitation caused by other risk factors.
authors.affiliation: Department of Internal Medicine, Section of Respiratory Medicine, Herlev and Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark Department of Public Health, Section of Social Medicine, University of Copenhagen, Copenhagen, Denmark The Copenhagen General Population Study, Herlev and Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Yunus
authors.initials: Y
authors.lastname: Çolak
authors.affiliation: The Copenhagen General Population Study, Herlev and Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark Department of Clinical Biochemistry, Herlev and Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark.
authors.forename: Shoaib
authors.initials: S
authors.lastname: Afzal
authors.affiliation: The Copenhagen General Population Study, Herlev and Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark Department of Clinical Biochemistry, Herlev and Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark.
authors.forename: Børge G
authors.initials: BG
authors.lastname: Nordestgaard
authors.affiliation: Department of Public Health, Section of Social Medicine, University of Copenhagen, Copenhagen, Denmark The Copenhagen General Population Study, Herlev and Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark Department of Clinical Biochemistry, Herlev and Gentofte Hospital, Copenhagen University Hospital, Herlev, Denmark Medical Unit, Respiratory Section, Hvidovre Hospital, Copenhagen University Hospital, Hvidovre, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Lange
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000402:Airway Obstruction / Q000453:epidemiology*; D001249:Asthma / Q000453:epidemiology*; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012129:Respiratory Function Tests; D012307:Risk Factors; D012907:Smoking
keywords: Asthma; Asthma Epidemiology; Asthma Mechanisms; COPD Exacerbations; COPD epidemiology; Clinical Epidemiology; Pneumonia; Smoking cessation