Association of prognostic nutritional index with mortality in patients with sepsis-associated delirium: a retrospective MIMIC-IV study

BACKGROUND: A concerning sign of severe brain dysfunction, sepsis-associated delirium (SAD) is associated with poor clinical outcomes. The prognostic value of the Prognostic Nutritional Index (PNI) for patients with SAD is unclear. OBJECTIVE: To determine the association between PNI and all-cause mortality at 90, 180, and 360 days in SAD patients. METHODS: We classified SAD patients into low-PNI and high-PNI groups based on PNI. We then used Kaplan-Meier (KM) survival analysis, multivariate Cox regression, restricted cubic spline (RCS) models, inverse probability of treatment weighting (IPTW), and subgroup analysis to evaluate the association between these groups and all-cause mortality at 90, 180, and 360 days. A receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive ability of PNI. RESULTS: Among 2,160 patients, the low PNI group had significantly higher mortality than the high PNI group at 90 days (51.9% vs. 33.5%), 180 days (56.4% vs. 37.1%), and 360 days (60.6% vs. 41.5%). After adjustment, Cox regression showed low PNI was associated with a 1.55-fold higher 90-day mortality (95% CI: 1.34-1.79, p < 0.001). A restricted cubic spline model revealed a nonlinear PNI-outcome relationship. These results were robust in IPTW and subgroup analyses, and ROC analysis demonstrated predictive performance comparable to that of SOFA and albumin. CONCLUSION: The PNI is a simple, useful, and easily accessible tool that can help identify patients with SAD who are at increased risk of adverse outcomes at an early stage.