Liver Aging Index: A Noninvasive Score for Liver Biological Aging and Liver-Related Outcomes in Multicohorts.

Biological aging is a key determinant of liver disease and mortality, but there is little evidence on noninvasive index for assessment of liver biological aging. We developed the Liver Aging Index (LAI) in the China Kadoorie Biobank (CKB, N = 21,629) using Cox-Gompertz proportional hazards model. The LAI incorporated three clinical factors (body mass index, systolic and diastolic blood pressure), eight plasma biomarkers (glucose, total cholesterol, triglycerides, high- and low-density lipoprotein cholesterol, alanine aminotransferase, aspartate aminotransferase, and γ-glutamyl transpeptidase), and two imaging biomarkers (fat attenuation parameter and liver stiffness measurement). External validation was conducted in the National Health and Nutrition Examination Survey (NHANES; N = 3412) and the VCTE-Prognosis cohort (N = 12,170, 16 global centers). Across all cohorts, the LAI demonstrated strong discrimination for all-cause mortality (AUROC: 0.764 in NHANES; 0.759 in VCTE-Prognosis), outperforming chronological age (p < 0.05). Liver aging acceleration (LAA), defined as the difference between LAI and chronological age, was associated with substantially elevated risks: each 1-SD increase in LAA conferred a 22%-85% higher risk of all-cause mortality and a 34%-170% higher risk of liver-related event or mortality. Using genetic instruments identified in CKB, we found genetic predisposition to accelerated liver aging was associated with higher risks of cirrhosis and liver cancer (HR = 3.94 [3.20-4.86] and 7.82 [2.05-29.80]), further validated in Biobank Japan. Integrating genetics and proteomics revealed novel pathophysiological involvement of amyloid-beta clearance pathway and amyloid precursor protein in liver aging. These findings demonstrate the feasibility of a noninvasive, liver-specific biological aging index and provide new insights into mechanisms underlying liver aging.