Liver Age Acceleration and Kidney Abnormalities Among Adult NHANES Participants: A Cross-Sectional Study

Background: Associations of liver age acceleration (LAA5), a model-derived hepatic composite, with kidney abnormalities remain unclear. We examined associations with a composite kidney outcome and its components. Methods: This survey-weighted cross-sectional analysis included 9276 complete cases among 14,608 adults aged ≥20 years examined in the National Health and Nutrition Examination Survey (NHANES) 2017–March 2020 Pre-Pandemic and August 2021–August 2023. LAA5 represented liver age estimated using the five-marker Liver Aging Index minus chronological age. Kidney abnormality was defined as urinary albumin-to-creatinine ratio ≥ 30 mg/g or creatinine-based estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2 at one examination. Logistic regression used examination (WTMECPRP) and phlebotomy (WTPH2YR) weights, respectively, adjusting for demographic, socioeconomic, adiposity, and lifestyle factors. Results: Overall, 1521 participants had kidney abnormality. In the primary model, each standard deviation (2.85 years) higher LAA5 was associated with higher odds of kidney abnormality (odds ratio [OR], 1.16; 95% confidence interval [CI], 1.08–1.25; p < 0.001) and albuminuria (OR, 1.21; 95% CI, 1.13–1.30; p < 0.001). The continuous reduced-eGFR estimate was inconclusive (OR, 1.08; 95% CI, 0.98–1.19; p = 0.103), with findings varying across exposure specifications and covariate imputation. Composite and albuminuria associations persisted after additional cardiometabolic adjustment and in missing-data analyses. Spline analyses provided no clear evidence of nonlinearity. Conclusions: Higher LAA5 was associated with kidney abnormality and albuminuria. Evidence for reduced eGFR was less consistent. Prediction of future kidney disease was not assessed. Selection bias remains possible. Prospective studies with repeated kidney measurements are needed to clarify longitudinal associations.