Inclusion Criteria:  Patients aged > 40 and < 80 years with post-bronchodilator FEV1/ forced vital capacity (FVC) < 0.7 and percentage predicted of FEV1>30%, who were no exacerbation of symptoms in the 6 weeks preceding the study, were included in the study.  Exclusion Criteria:  Patients who were diagnosed with other chronic respiratory diseases, including bronchial asthma, bronchiectasis and lung abscess. Patients with near-terminal illness, congestive heart failure (NYHA III-IV), or cannot record CAT score timely were excluded.