IL6 and chronic obstructive pulmonary disease: Network meta-analysis showed that the SUCRA of reducing the IL-6 in COPD patients in Atorvastatin, Fluvastatin, Rosuvastatin, Pravastatin and Simvastatin were 52.7, 25.5, 70.7, 58.3 and 79.9%, respectively (Additional file 7: Table S1 and Additional file 8: Figure S7).