Geriatric nutritional risk index and prognostic nutritional index improves predictive value of postoperative mortality: a large-scale retrospective cohort study.

Background: Malnutrition increases the risk of mortality. However, the predictive role of preoperative nutritional status in postoperative mortality remains underexplored. This study investigates the link between preoperative objective nutritional indices and postoperative mortality across all adult surgical patients and evaluates the predictive value of malnutrition for postoperative mortality.

Methods: This retrospective study included patients aged 18 or older who underwent surgery. Nutritional status was assessed using the Geriatric Nutritional Risk Index (GNRI) and the Prognostic Nutritional Index (PNI). Logistic regression analysis was performed to explore the relationship between preoperative nutritional status and postoperative mortality and to evaluate the predictive value of nutrition scores for mortality.

Results: The study included 79,648 patients. Among them, 12,392 (15.6%) were identified with malnutrition by GNRI, 13,773 (17.3%), by PNI, and 8,633 (10.8%) by both indices. A total of 276 patients died within 30 days after surgery. After adjusting for traditional risk factors, poorer nutritional scores were linked to increased mortality risk. GNRI and PNI also enhanced the predictive accuracy of postoperative mortality models, as evidenced by significant improvements in integrated discrimination and net reclassification.

Conclusions: Poor preoperative nutritional status, as indicated by GNRI and PNI scores, is associated with a higher risk of postoperative mortality. Integrating these scores into mortality prediction models significantly enhances their accuracy. These findings highlight the importance of screening surgical patients for malnutrition risk to inform perioperative nutritional management.

Trial registration: The Institutional Review Board (IRB) of Seoul National University Hospital No. H-2210-078-1368).