Main differentiating and overlapping features of asthma and COPD

FeatureAsthmaCOPDExceptions and overlapping features
Risk factorsAllergensSmokingSmoking may be an aggravating factor in asthma; children with early-life wheezing have a higher risk of developing asthma as teenagers and chronic obstructive pulmonary disease (COPD) as adults (the “Dutch hypothesis”); repeated airway infections may trigger development of either asthma or COPD, depending on the nature of infection and the intrinsic genetic predisposition (the “British hypothesis”)
Anatomic segment involvedAirwaysAirways and parenchymaSevere asthma exacerbations may lead to adjacent parenchymal destruction, severe hyperinflation, and loss of scaffolding, or to radial or axial traction, or both, on the small airways
AtopyYesNoAtopy may be present in some patients with COPD
Airway inflammationYesYesAbsent in mild asthma between exacerbations
Peripheral eosinophiliaYesNoSome patients with COPD may have eosinophilia; some patients with asthma may have neutrophilic infiltration (eg, severe asthma, asthma coexistent with gastroesophageal reflux and chronic rhinitis)
Airway eosinophiliaYesNo20%–40% of patients with COPD have airway eosinophilia (if one excludes eosinophilic bronchitis, up to 20% patients with COPD can still have some eosinophilic airway infiltration)
Exhaled gas (lower-airway) nitric oxide concentrationHighLowMay be reduced in some asthma phenotypes, eg, neutrophilic or paucigranulocytic; may be present in some patients with COPD
Diffusing lung capacity for carbon monoxideNormalReduced (in emphysema)Normal in chronic bronchitis; increased in acute asthma
Airway resistanceHighHighNormal in mild asthma between exacerbations; normal or slightly increased in emphysema
Airway hyperresponsivenessYesNoMay be present in COPD
Elastic recoil of the airways and parenchymaNormalReduced (in emphysema)Reduced in acute exacerbations of severe asthma; normal in chronic bronchitis
SymptomsEpisodicPersistentMay be episodic in some patients with COPD, especially during significant environmental exposures
ComorbiditiesAtopic dermatitis, allergic rhinitisCardiovascular diseaseObstructive sleep apnea may complicate both conditions