Association of a body shape index (ABSI) with chronic kidney disease prevalence, all-cause and cardiovascular mortality: A 20-year prospective cohort study of 29,189 U.S. adults.

BACKGROUND

Conventional obesity metrics like body mass index (BMI) and waist circumference (WC) inadequately assess visceral adiposity and mortality risks in chronic kidney disease (CKD) populations. The A Body Shape Index (ABSI), which normalizes WC for height and body mass, may better capture central adiposity and CKD-related risks, yet its prognostic value remains underexplored. This study evaluates ABSI's association with CKD prevalence, all-cause mortality, and cardiovascular disease (CVD) mortality compared to traditional and novel anthropometric indices.

METHODS

This prospective cohort study utilized data from the National Health and Nutrition Examination Survey (NHANES 1999-2018). The primary cohort included 29 189 U.S. adults to evaluate associations of abdominal obesity indices with CKD risk. Within this cohort, a subgroup of 4739 adults with CKD was subsequently analyzed for associations with all-cause and CVD mortality. A Body Shape Index (ABSI), waist-to-height ratio (WHTR), and body roundness index (BRI) were calculated and standardized using sex-specific z-scores. CKD was defined per Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Cox proportional hazards models, restricted cubic splines (RCS), and time-dependent receiver operating characteristics (ROC) analyses were employed to assess outcome associations, with adjustments for sociodemographic, clinical, and metabolic covariates.

RESULTS

Over a 20-year follow-up, ABSI demonstrated relatively higher discrimination for CKD prevalence [adjusted odds ratio (OR) per standard deviation (SD) increase: 1.20, 95% confidence interval (CI): 1.14-1.26] and mortality compared to other indices. Fully adjusted models revealed dose-dependent associations: the highest ABSI quartile (Q4) had 45% higher all-cause mortality [hazard ratio (HR): 1.45, 95% CI: 1.17-1.80] and 79% increased CVD mortality (HR: 1.79, 95% CI: 1.15-2.80) versus Q1. Nonlinear thresholds identified critical inflection points (ABSI z-scores >0.858 for all-cause mortality; >0.542 for CVD mortality). ROC analyses showed ABSI's comparatively higher AUC values: all-cause mortality AUC = 0.67 (95% CI: 0.66-0.69) and CVD mortality AUC = 0.64 (95% CI: 0.61-0.66) versus WHTR/BRI AUC values of -0.51 to 0.52. Subgroup analyses highlighted heightened ABSI-associated risks in adults >60 years (CVD mortality HR: 2.58, 95% CI: 1.31-5.09) and sex-specific disparities, with males exhibiting lower mortality risks at elevated ABSI levels.

CONCLUSIONS

ABSI showed stronger associations and relatively better discrimination than conventional adiposity indices in CKD risk stratification and mortality prediction, particularly in older adults. Identified thresholds offer actionable targets for clinical monitoring. These findings suggest ABSI's potential utility in refining obesity-related risk assessment in CKD populations, meriting further investigation of its clinical applicability.