Preoperative Prognostic Nutritional Index Value is Related to Postoperative Delirium in Elderly Patients After Noncardiac Surgery: A Retrospective Cohort Study

PURPOSE: Malnutrition has been considered as a risk factor for postoperative delirium (POD). The Prognostic Nutritional Index (PNI) is a validated tool for assessing nutritional status. This study aimed to investigate the association between preoperative PNI values and the occurrence of POD in elderly surgical patients. METHODS: The retrospective cohort study included 361 elderly individuals who underwent noncardiac surgery between 2018 and 2019. Perioperative data were collected from the patients’ medical records. PNI was used to evaluate preoperative nutritional status. The primary outcome was the occurrence of POD. Univariate and multivariate logistic regression analyses were used to identify key factors associated with POD and assess the relationship between PNI values and the occurrence of POD. Receiver operating characteristic (ROC) curve analysis was used to assess the predictive value of PNI for POD. RESULTS: Seventy-two (19.9%) individuals developed postoperative delirium after surgery. Compared with patients of normal nutrition status (PNI ≥ 50), mild malnutrition (PNI 45–50) did not increase the risk of POD, while patients with moderate to severe malnutrition (PNI 40–45) (odds ratio [OR], 2.92; 95% confidence interval [CI], 1.31–6.50) and serious malnutrition (PNI < 40) (OR, 3.15; 95% CI, 1.12–8.83) were more likely to develop POD. The cut-off value of PNI was 46.05 by ROC curve analysis, the area under the curve (AUC) was 0.69 (95% CI 0.62–0.77). CONCLUSION: Preoperative PNI value is related to postoperative delirium in elderly patients after noncardiac surgery.