Risk factors |
Increased age |
Severity of FEV1 impairment |
Chronic bronchial mucus hypersecretion |
Frequent past exacerbations |
Daily cough and wheeze |
Persistent symptoms of chronic bronchitis |
Comorbid conditions: mainly cardiovascular disease |
FEV1: forced expiratory volume in 1 s. Adapted from [11–14, 17, 18].