Association between preoperative prognostic nutritional index and postoperative delirium in older adults with hip fractures: a real-world study.

BACKGROUND: The prognostic nutritional index (PNI), a marker reflecting nutritional and immunological status, has been proposed as a predictor of adverse postoperative outcomes. However, whether its association with postoperative delirium (POD) differs between femoral neck fractures and intertrochanteric fractures remains unclear.

METHODS: This retrospective cohort study included patients aged ≥60 years who underwent hip fracture surgery between 2023 and 2024 PNI was calculated preoperatively, and POD was diagnosed during hospitalization using standardized clinical criteria. Analyses were conducted separately for femoral neck and intertrochanteric fracture groups for comparison. Restricted cubic spline (RCS), cox regression, subgroup analyses, receiver operating characteristic (ROC), propensity score matching (PSM), and Kaplan-Meier analyses were performed.

RESULTS: A total of 339 patients with femoral neck fractures and 260 patients with intertrochanteric fractures were included in this study. A significant association between preoperative PNI and POD was observed in patients with femoral neck fractures. In patients with femoral neck fractures, RCS analysis demonstrated an approximately linear inverse relationship between PNI and POD risk (p for trend < 0.001). In Cox proportional hazards models, each one-unit increase in PNI was associated with a 24% reduction in the risk of POD (HR = 0.76, 95% CI: 0.66-0.88, p < 0.001). ROC curve analysis indicated moderate predictive performance(AUC = 0.699).Sensitivity analyses confirmed the robustness of the association.

CONCLUSION: A lower preoperative PNI was associated with an increased risk of POD among older adults with femoral neck fractures, but not among those with intertrochanteric fractures. PNI may serve as a simple tool for preoperative risk stratification in patients with femoral neck fractures.