Comparative associations of waist circumference and body-mass index with reduced kidney function in patients with type 2 diabetes mellitus

Aims: Central obesity may better reflect metabolic risk than general obesity in adults with type 2 diabetes mellitus (T2DM). This study compared the associations of waist circumference (WC) and body-mass index (BMI) with reduced kidney function. Methods: This retrospective, cross-sectional study included 300 adults with T2DM. Demographic, anthropometric, clinical, and laboratory data were obtained from electronic medical records. Reduced kidney function was defined as an estimated glomerular filtration rate (eGFR)<60 ml/min/1.73 m². Spearman correlation, receiver operating characteristic (ROC) curve, and multivariable logistic regression analyses were performed. Results: Reduced kidney function was identified in 46 (15.3%) patients. WC was inversely correlated with eGFR (ρ=-0.152, p=0.008), whereas BMI was not (ρ=-0.054, p=0.356). Patients with reduced kidney function had greater WC (p=0.016), while BMI was similar between groups (p=0.399). WC showed better discrimination than BMI (AUC: 0.612 vs. 0.539). After adjustment for age, gender, diabetes duration, HbA1c, and systolic blood pressure, WC remained independently associated with reduced kidney function (OR 1.026, 95% CI 1.001-1.052, p=0.045), whereas BMI did not. Conclusion: WC showed a stronger association with reduced kidney function than BMI in adults with T2DM. Although its discriminatory performance was modest, WC remained independently associated with reduced kidney function after adjustment for established clinical risk factors. Routine assessment of WC may provide clinically useful information beyond BMI for identifying patients at increased risk of reduced kidney function.