IL6 and obstructive sleep apnea syndrome: In the same vein, several recent meta-analyses reported the association between the risk of OSA and specific polymorphisms, such as interleukin (IL)-6, leptin receptor, and matrix metalloproteinase-9 [15,16,17], blood levels of biomarkers such as adiponectin, C-reactive protein, IL-6, and cortisol [18,19,20,21], smoking [22,23], along with greater alcohol and caffeine consumption [23].