Geriatric nutritional risk Index predicts adverse outcomes across cardiovascular-kidney-metabolic syndrome: discovery in NHANES and external validation in CKM stage 4 patients undergoing PCI.

In the discovery cohort, compared with the highest Geriatric Nutritional Risk Index quartile (Q4), Q1 was associated with significantly higher hazards of all-cause (HR 1.58; 95% CI 1.32-1.89) and cardiovascular mortality (HR 2.13; 95% CI 1.55-2.93); each 1-unit increase in Geriatric Nutritional Risk Index was associated with a lower hazard of all-cause mortality (HR 0.95; 95% CI 0.94-0.97).

Restricted cubic splines revealed a non-linear inverse relationship, with risk rising sharply below Geriatric Nutritional Risk Index ≈ 100.

Adding Geriatric Nutritional Risk Index to a base clinical model significantly improved Harrell's C-index for MACE (Δ +0.048, P < 0.001) with excellent calibration.