Body Mass Index, Coronary Artery Calcification, and Kidney Function Decline in Stage 3 to 5 Chronic Kidney Disease Patients

Objective To determine whether body mass index (BMI) and coronary artery calcification (CAC) are risk factors for kidney function decline in predialysis chronic kidney disease (CKD) patients. Design Prospective cohort study of 125 stage 3 to 5 predialysis CKD patients. Subjects and Setting CKD patients receiving care in Kingston, Ontario, Canada. Methods BMI, CAC, and kidney function were measured at baseline. CAC was measured by multislice computed tomography scan. Kidney function was determined by the 4-variable reexpressed Modification of Diet in Renal Disease Study equation. At study end, kidney function decline among patients was compared according to baseline BMI and CAC. Main Outcome Kidney function decline was defined as a 1-year decline in estimated glomerular filtration rate (eGFR) of ≥5%. Results Individuals with a decline in eGFR of ≥5% at 1 year had higher baseline BMI (33.5 ± 8.3 vs. 28.4 ± 4.9 kg/m2 ; P = .0001) and higher baseline median CAC scores (239 vs. 25 Agatston units; P = .01) compared with subjects without such a decline. BMI ( r = 0.35; P < .0001) and logarithmically transformed CAC score ( r = 0.22; P = .01) correlated with an eGFR decline of ≥5%. Both crude and adjusted logistic regression analyses showed escalating CAC (with CAC reported in quintiles and CAC score = 0 Agatston unit as the reference group) was associated with an increased risk of eGFR decline of ≥5%. Conclusions CAC and BMI were associated with kidney function decline over 1 year. The risk of kidney function decline was greater in those with increasing burden of CAC, which remained robust in the adjusted analysis accounting for the risk factors for CKD progression. Larger studies will be required for independent validation of the associations of BMI, CAC, and kidney function decline, and to investigate whether obesity and CAC treatment strategies are efficacious in attenuating kidney function decline in predialysis CKD patients.