IL6 and obstructive sleep apnea syndrome: Specifically, it has been seen that CPAP treatment significantly reduces the levels of endothelin-1 (long-acting vasoconstrictor peptide), interleukin-6 (IL-6), C-reactive protein (heightened inflammatory states) and erythropoietin (elevated in procoagulant states) compared to untreated OSA patients [46,52,61].