Participants
COPD
MAY, COPD
Participants were recruited from May 2022 to July 2022. Inclusion criteria were as follows: (1) the diagnosis of stable COPD patients according to the GOLD (2022) guidelines, with a postbronchodilator ratio of the forced expiratory volume in one second (FEV1) to the forced vital capacity (FVC) < 0.70, and absence of exacerbation in the 4 weeks before collection