Body roundness index and mortality risk in patients with chronic kidney disease: moving beyond the obesity paradox

BACKGROUND: Body roundness index (BRI), an emerging anthropometric measure, has been shown to outperform body mass index (BMI) in predicting mortality risk in the general population. However, its prognostic value among patients with chronic kidney disease (CKD), where the obesity paradox may exist, remains unknown. METHODS: This observational study utilized data from the National Health and Nutrition Examination Survey. BRI was calculated using waist circumference (WC) and height, whereas BMI was calculated using body weight and height. Restricted cubic splines were applied to determine optimal cutoff points of BRI for all-cause and cardiovascular mortality in patients with CKD. Associations were examined using Cox proportional hazards models adjusted for potential confounders. RESULTS: Over a median follow-up of 6.6 years, 6 240 patients with CKD (mean age: 63 years, 43% men) were included, with 1 922 all-cause and 715 cardiovascular deaths recorded. RCS demonstrated J-shaped associations between BRI with mortality. A BRI > 10 was associated with significantly increased risk of all-cause [adjusted hazard ratio (aHR): 1.82, 95%CI: 1.34-2.47] and cardiovascular mortality (aHR: 2.15, 95%CI: 1.27-3.62) compared to reference of 5.9-6.8 and 5.9-6.5, respectively, with dose-response trends (P for trend < 0.05). A BMI > 30 was paradoxically associated with 44% and 40% lower risks of all-cause and cardiovascular mortality compared to reference of 18.5-25, respectively. A WC> 125 cm was associated with increased risk of all-cause mortality (aHR: 2.17, 95%CI: 1.47-3.18), but not with cardiovascular mortality (aHR: 1.83, 95%CI: 0.97-3.45), compared to reference of 95-105 cm. The associations between BRI > 10 and mortality risks were particularly pronounced among younger adults aged < 65 years or individuals with elevated albuminuria (P for interaction < 0.05). CONCLUSIONS: Higher BRI was independently associated with increased all-cause and cardiovascular mortality risk among patients with CKD, offering greater prognostic value for risk stratification than BMI or WC.