# Association between weight-adjusted waist index and risk of mortality and disease progression in participants with chronic kidney disease: a prospective study from the UK Biobank

## TL;DR

This study shows that a new measure of central obesity, the weight-adjusted waist index, is linked to higher risks of death and kidney disease progression in people with chronic kidney disease.

## Contribution

The study introduces the weight-adjusted waist index as a novel obesity metric with better predictive power than BMI or waist circumference in CKD patients.

## Key findings

- WWI showed non-linear associations with all-cause mortality and ESKD, and a linear association with CVD mortality.
- WWI values above 10.5 cm/√kg were significantly linked to worse outcomes in CKD patients.
- WWI outperformed BMI and waist circumference in predicting all-cause mortality, though its overall discriminative power was modest.

## Abstract

The weight-adjusted waist index (WWI), a novel metric reflecting central obesity, has shown potential as a predictor of adverse health outcomes. This study investigated the associations between WWI and all-cause mortality, cardiovascular disease (CVD) mortality, and the incidence of end-stage kidney disease (ESKD) among participants with chronic kidney disease (CKD), and further compared its predictive performance with that of conventional obesity indices.

This prospective cohort study was conducted with data from the United Kingdom Biobank (UKB). Participants with CKD at baseline were included, while those with ESKD, missing data on WWI or other obesity indicators, or incomplete covariate information were excluded. Follow-up time was calculated from the baseline to the occurrence of disease diagnoses, surgical interventions, mortality or the censoring date (31 December 2021). CKD was diagnosed using baseline clinical data, and WWI was calculated as the waist circumference (WC, cm) divided by the square root of body weight (kg). Cox proportional hazards models and restricted cubic spline (RCS) analysis were employed to examine the associations between WWI and all outcomes. Receiver operating characteristic (ROC) curve analysis were conducted to compare the predictive performance of WWI, body mass index (BMI) and WC.

During a follow-up period of 269,858.2 person-years for 22,523 participants, 3,874 all-cause deaths, 786 CVD deaths and 823 ESKD events were recorded. WWI exhibited non-linear association with all-cause mortality and ESKD incidence (P for non-linear < 0.001), and linear association with CVD mortality (P for non-linear = 0.175). WWI values above the threshold (10.5 cm/√kg) showed significant positive associations with all outcomes (all P value < 0.001). WWI demonstrated superior overall predictive performance compared with traditional obesity indicators, particularly in predicting all-cause mortality.

These findings suggest that an elevated WWI is associated with an increased risk of all-cause mortality, CVD mortality and ESKD in patients with CKD, particularly in high WWI groups. Although WWI demonstrated statistically superior discriminatory performance compared with BMI and WC, its overall discriminative capacity remained modest. Accordingly, WWI may serve as a complementary anthropometric indicator for risk assessment in CKD, further studies are required to establish its clinical applicability.