Table 2.

Differences between asthma and chronic obstructive pulmonary disease (COPD)^*

Characteristic	Asthma	COPD
Age at onset	Usually < 40 yr	Usually > 40 yr
Smoking history	Not causal, but worsens control	Usually >10 pack-years
Sputum production	Infrequent	Common
Allergies	Common	Infrequent
Clinical symptoms	Intermittent and variable	Persistent and progressive
Course of disease	Stable (with exacerbations)	Progressive worsening (with exacerbations)
Importance of nonrespiratory comorbid illnesses	Not usually important	Often important
Spirometry results	Often normalize over time	May improve, but do not normalize over time
Airway inflammation	Eosinophilic	Neutrophilic

^*Adapted with permission from the Canadian Pharmacists Journal: 140[Suppl 3], 2007.²²