IL6 and chronic obstructive pulmonary disease: It was found that COPD patients with an FEV1 either <50% predicted or >50% predicted had increased IL-6 concentrations compared with healthy control subjects (SMD = 0.77, 95% CI [0.48–1.05], P < 0.00001; I2 = 29%, P = 0.19; SMD = 1.01, 95% CI [0.43–1.59], P = 0.0006; I2 = 77%, P = 0.0007, respectively; Fig. 4).