Transcripts of BMAL1 (p = 0.005, η2 = 0.097), CK1ε (p = 0.003, η2 = 0.102), CLOCK (p = 0.004, η2 = 0.100), CRY1 (p = 0.005, η2 = 0.095), CRY2 (p = 0.002, η2 = 0.105), PER2 (p = 0.003, η2 = 0.103), PER3 (p < 0.001, η2 = 0.147), and TIM (p = 0.043, η2 = 0.062) were significantly downregulated at 12 AM in the severe group of patients with OSA (Figure 3A–E,G–I). Here, PER3 is linked to obstructive sleep apnea syndrome.