BDNF and obstructive sleep apnea syndrome: In the OSA group, morning BDNF and proBDNF protein levels correlated with age (r = −0.608, p = 0.004 and r = −0.539, p = 0.014, respectively), morning HIF-1α protein level (r = −0.426, p = 0.041 and r = −0.603, p = 0.005, respectively), TST (r = 0.623, p = 0.003, and r = 0.388, p = 0.041, respectively), basal SpO2 level (r = −0.679, p = 0.001 and r = −0.464, p = 0.039, respectively), as well as the mean SpO2 of desaturations during sleep (r = −0.585, p = 0.039 and r = −0.397, p = 0.043, respectively).