Objective:To evaluate the relationship between postoperative delirium(POD) and preoperative frailty in elderly patients undergoing spinal surgery.Methods:Two hundred and twenty patients of both sexes, aged ≥65 yr, of American Society of Anesthesiologists Physical Status classification Ⅱ-Ⅳ, undergoing elective posterior lumbar decompression, bone grafting and internal fixation under general anesthesia, were selected. Frailty was measured using the FRAIL (fatigue, resistance, ambulation, illness, and loss of weight) scale on 1 day before surgery. POD was assessed twice a day within 3 days by Confusion Assessment Method. Patients were divided into POD group and non-POD group according to whether POD occurred within 3 days after surgery. Multivariate logistic regression analysis was used to identify the risk factors for POD in elderly patients undergoing spinal surgery, and the value of preoperative frailty in predicting POD was analyzed using the receiver operating characteristic curve.Results:A total of 190 patients were finally enrolled, among which 55 patients presented with frailty before surgery, and the incidence was 29.0%. Forty-six patients developed POD, and the incidence was 24.2%. Multivariate logistic regression analysis showed that aging ( OR=1.15, 95% confidence interval [ CI] 1.03-1.29, P=0.017), preoperative frailty ( OR=2.35, 95% CI 1.24-4.43, P=0.009), increase in surgical segments ( OR=4.14, 95% CI 1.71-10.05, P=0.002) and increase in postoperative 24-h pain VAS score ( OR=1.38, 95% CI 1.07-1.78, P=0.013) were independent risk factors for POD in elderly patients undergoing spinal surgery. The area under receiver operating characteristic curve of preoperative frailty in predicting POD was 0.702 (95% CI 0.608-0.796, P<0.001). Conclusions:Preoperative frailty is an independent risk factor for POD in elderly patients undergoing spinal surgery. Preoperative frailty can predict the occurrence of POD in elderly patients undergoing spinal surgery to some extent.