Association between prognostic nutritional index and poor prognosis in elderly critically ill patients with heart...

Background: heart failure (HF) poses a significant global health burden, particularly in the elderly population whose prognosis remains poor. The prognostic nutritional index (PNI), a composite marker of nutritional and immune status, has not been adequately evaluated in critically ill elderly HF patients. This study aimed to assess the association between PNI and outcomes in this high-risk population. Methods: a retrospective cohort of elderly HF patients with measured PNI was identified from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. The primary outcomes included mortality at 30, 60, and 90 days. The association between PNI and survival outcomes was evaluated using multivariate Cox proportional regression. Receiver operating characteristic (ROC) curve analysis was performed to compare the discriminatory ability of PNI with SOFA and OASIS scores. Further validation was conducted through Kaplan-Meier survival analysis, restricted cubic spline fitting, and subgroup analyses. Results: a total of 1982 patients were included in this study. Those with higher PNI had a 4 % decreased risk of 30-day mortality (HR 0.96, 95 % CI 0.95-0.97, p < 0.01), which remained consistent for 60-day and 90-day mortality. When patients were stratified into three distinct groups based on PNI tertiles, Kaplan-Meier curves consistently demonstrated a graded inverse association between PNI levels and survival probability, with the lowest tertile exhibiting the poorest prognosis (log-rank p < 0.01). Restricted cubic spline analyses revealed a consistent monotonic decreasing relationship between PNI and mortality risk at 30, 60, and 90 days. The association remained robust across most subgroups, although the protective effect of PNI appeared attenuated in patients with cerebrovascular disease (HR 0.97, 95 % CI 0.94-1.01, p = 0.19). Conclusions: in elderly critically ill HF patients, lower admission PNI is independently associated with higher mortality risk, supporting its utility for early risk stratification in ICU settings. However, its prognostic value may be limited in patients with comorbid cerebrovascular disease. Further prospective, multicenter studies are required to validate these findings.