IL6 and chronic obstructive pulmonary disease: The mean serum levels of NE and IL‐6 were significantly higher in the COPD‐S group than in the healthy‐S group (NE: 69.29 versus 46.89 ng/ml, respectively, P = 0.006; IL‐6: 3.13 versus 2.25 pg/ml, respectively; P = 0.001, both in a Mann–Whitney U‐test).