Association between the geriatric nutritional risk index and all-cause mortality in patients with acute pancreatitis in the intensive care unit: a retrospective cohort study

Critical illness complicates acute pancreatitis (AP) with acute malnutrition, which increases mortality. The Geriatric Nutritional Risk Index (GNRI) integrates serum albumin and body weight, but its short-term, intermediate-term, and long-term mortality prognostic value in AP admitted to the ICU remains unclear. A retrospective cohort study including 430 adults with a first ICU admission for AP. The primary outcome was 28-day all-cause mortality; secondary outcomes were 90- and 360-day mortality. Multivariable Cox regression, restricted cubic splines (RCS) and Kaplan–Meier analyses were used to assess linear and non-linear associations; effect modification was examined in prespecified subgroups. Median GNRI was 83.4. Each 1-unit increment reduced 28-day mortality by 6% (HR 0.94, 95% CI 0.91–0.97, P = 0.001) with similar effect sizes at 90 and 360 days. RCS revealed a J-shaped curve with a nadir at ≈ 86.8: below this threshold each unit decrease increased risk by 10.4%, whereas above its risk rose by 24.2%. The high-GNRI group had a 62% lower 28-day mortality than the low-GNRI group (HR 0.38, 95% CI 0.21–0.70, P = 0.002). Survival curves remained significantly separated (log-rank P = 0.0018). Subgroup analyses showed stronger protection in males and patients < 60 years (P-interaction < 0.05). GNRI is a rapid, objective and non-linear predictor of short-term, intermediate-term, and long-term mortality in critically ill AP. The J-shaped association supports early nutritional inflammatory risk stratification. Further prospective studies should assess the utility of the GNRI to guide nutritional support interventions in this patient population.