Fig. 2From: An observational study of the effects of smoking cessation earlier on the clinical characteristics and course of acute exacerbations of chronic obstructive pulmonary diseaseProportion of patients with different (A) GOLD grade classification, (B) cough severity, (C) mMRC score, and (D) phlegm severity. **P < 0.01, and ***P < 0.001Back to article page