CD4 and sleep apnea syndrome: ATG5 protein expression of blood monocyte was decreased in SDB patients with daytime fatigue versus those without daytime fatigue (2.26 ± 2.36 versus 4.12 ± 3.33, adjusted p = 0.025, Fig. 1G), and ATG5( +) percentage of blood CD3+CD4+ helper T cell was negatively correlated with arousal index (R = − 0.258, p = 0.038, Fig. 1H).