Abstract: Objective To evaluate the predictive value of preoperative frailty for chronic post-sugrical pain (CPSP) in elderly patients in department of thoracic surgery. 
Methods In total, 318 patients underwent elective thoracic surgery under general anesthesia, who were aged 65 years or older, with American society of anesthesiologists (ASA) Ⅱ-Ⅳ and regardless of gender. Frailty was assessed using FRAIL Scale at 1 d before surgery. At 24 h and 48 h after surgery, the numerical rating scale (NRS) was used to record patient pain scores at rest and on movement, and telephone follow-up was performed at 3 months after surgery, to record the patient's pain scores. NRS score＞0 represented the occurrence of CPSP. Patients were divided into CPSP and non-CPSP groups based on whether CPSP occurred at 3 months after surgery. Multivariate Logistics regression analysis was used to screen risk factors for CPSP in elderly patients undergoing thoracic surgery and receiver operating characteristic (ROC) curve was used to analyze the predictive value of preoperative frailty on CPSP. 
Results Of 273 patients enrolled, 64 patients had preoperative frailty, with an incidence of 23.4%, and 75 patients developed CPSP, with an incidence of 27.5%. Univariate Logistic regression results showed that there were significant differences in both groups with respect to gender, age, ASA grade, diabetes, duration of thoracic drainage, mean NRS score at rest at 48 h after surgery, number of incisions and frailty grade. The results of multivariate Logistics regression analysis showed that female （OR 2.545, 95%CI： 1.365-4.746, P=0.003）, preoperative frailty （OR 3.272, 95%CI： 2.146-4.853, P＜0.001）, duration of thoracic drainage （OR 1.250, 95%CI： 1.079-1.449, P= 0.003） and the mean NRS score at rest at 48 h after surgery （OR value 1.457, 95%CI： 1.081-1.963, P=0.014） were closely related with occurrence of CPSP in elderly patients undergoing thoracic surgery. The area under the ROC curve (AUC) of preoperative frailty in predicting CPSP was 0.705, with 95%CI： 0.634-0.776, sensitivity of 0.493, specificity of 0.843. 
Conclusion Female gender, preoperative frailty, prolonged time of thoracic drainage and elevated mean NRS score at rest at 48 h after surgery are independent risk factors for CPSP in elderly patients undergoing thoracic surgery. Routine preoperative frailty screening can predict the occurrence of CPSP to some extent. 

Key words: frailty, pain, postoperative, Elderly