A total of 292 elderlypatients of both sexes, aged 65-90 yr, weighing 50-90 kg, of American Society of Anesthesiologists physical status Ⅰ-Ⅱ, with Mini-Mental State Examination (MMSE) score>23 and Montreal Cognitive Assessment (MoCA) score > 26 at 1 day before operation, underwent total knee/hiparthroplasty under combined spinal-epidural block in our hospital from January to December 2020, were collected.The development of SCD was evaluated using subjective cognitive decline scale at 1 day before operation.Cerebrospinal fluid (CSF) was extracted after successful spinal-epidural anesthesiapuncture, the concentrations of β-amyloid protein 40 (Aβ 40), Aβ 42, total tau (t-tau) and phosphorylated tau (p-tau) were determined by enzyme-linked immunosorbent assay.The incidence of POD was evaluated using confusion assessment method during post-anesthesia care unit and at 1-7 days after operation (or before discharge). Patients were divided into POD group and non-POD group according to whether POD occurred within 7 days after operation.The risk factors of which P values were less than 0.05 would enter the logistic regressionanalysis to stratify the risk factor for incidence of POD.