CRP and chronic obstructive pulmonary disease: In the OS group, the serum levels of D-dimer, C-reactive protein (CRP), cardiac troponin T (cTnT), and lactate dehydrogenase (LDH) were higher than those in the OSAS group (all p < 0.001); and the serum levels of triglyceride and low-density lipoprotein (LDL) were higher than those in the COPD group (all p < 0.001).