Binary logistic regression analysis selected CRY1 and PER3 as independent factors for severe OSA and showed that the combined expressions of CRY1 and PER3 enhanced the capability of predicting severe OSA (Odds ratio, 5.800; 95% CI, 1.978 to 17.004; p = 0.001). The gene discussed is CRY1; the disease is obstructive sleep apnea syndrome.