IL6 and obstructive sleep apnea syndrome: OSA (Vgontzas et al., 1997; Liu et al., 2000; Li et al., 2017; Motamedi et al., 2018), insomnia (Vgontzas et al., 2002), and narcolepsy (Okun et al., 2004) have also been associated with increased serum IL-6 levels.