PER3 and obstructive sleep apnea syndrome: Binary logistic regression analysis selected CRY1 (Odds ratio, 2.963; 95% CI, 1.277 to 6.879; p = 0.011) and PER3 (Odds ratio, 3.746; 95% CI, 1.595 to 8.795; p = 0.002) as independent factors for severe OSA (Table 2).