IL6 and obstructive sleep apnea syndrome: Other studies on obstructive sleep apnea syndrome suggested that patients with obstructive sleep apnea syndrome showed high serum levels of tumor necrosis factor-α (TNF-α), IL-6, CRP, and spontaneous production of IL-6 by monocytes compared with obese control subjects (Vgontzas et al., 2000; Yokoe et al., 2003).