Association Between Preoperative Prognostic Nutritional Index and Delirium After Spine Surgery in the Elderly: A Retrospective Analysis.

STUDY DESIGN: This is a retrospective case-control study. OBJECTIVE: This study hypothesized that a low preoperative prognostic nutritional index (PNI) would increase the risk of postoperative delirium in such patients and aimed to prove it. SUMMARY OF BACKGROUND DATA: Postoperative delirium in elderly patients results in prolonged hospitalization and an increased burden of medical costs. Preoperative PNI is associated with perioperative adverse outcomes following major surgery. However, its independent association with postoperative delirium remains underexplored in elderly patients undergoing spine surgery. METHODS: Perioperative data of 711 patients (age 65 y or older) who underwent spine surgery were retrospectively analyzed. Based on the optimal cutoff value (47.8) of preoperative PNI, patients were classified into the high (n=512) and the low (n=199) PNI groups. To balance baseline characteristics between the 2 groups, stabilized inverse probability weighting (SIPW) was applied, and logistic regression analysis was performed to evaluate the relationships between preoperative PNI and postoperative delirium. RESULTS: Postoperative delirium developed in 40/711 (5.6%) patients. The incidence of postoperative delirium was markedly higher in the low PNI group than in the high PNI group both before [25 (12.6%) vs. 15 (2.9%), P<0.001] and after [20 (10.1%) vs. 15 (2.9%), P<0.001] SIPW. In logistic regression analysis after SIPW, preoperative PNI <47.8 was associated with increased risk of postoperative delirium [adjusted odds ratio: 3.57 (95% CI: 1.80-7.09), P<0.001]. CONCLUSIONS: A low preoperative PNI is an independent predictor of postoperative delirium in elderly patients undergoing spine surgery.