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

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. To determine the association between PNI and all-cause mortality at 90, 180, and 360 days in SAD patients. 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. 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. 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.