CRP and chronic obstructive pulmonary disease: Table 2 summarizes the characteristics of patients with COPD with and without OSA of the training group and the validation group. Patients in both OSA groups revealed a higher proportion of hypertension, type 2 diabetes, and coronary heart disease; higher BMI, NC, SACS; lower CRP, mMRC, and CAT; as well as poorer polysomnographic data and less AE (all p < 0.05). The differences in airflow limitation between OS and COPD groups in training and validation groups were statistically significant (p < 0.05).