Comparison between Different Measures of Body Fat with Kidney Function Decline and Incident CKD

Although anthropometric measures of body fat are associated with development of CKD, they may not be able to distinguish between various forms of fat and therefore may be less accurate than computed tomography (CT) measures. We compared the association of CT and anthropometric measures of obesity with kidney outcomes in the Health Aging and Body Composition Study.

Participants were recruited from March of 1997 through July of 1998. CT measures included visceral abdominal fat (VAT), subcutaneous adipose tissue (SAT), and intermuscular fat area (IMAT), whereas anthropometric measures included waist circumference (WC) and body mass index (BMI). Kidney outcomes included kidney function (KF) decline (30% decrease in eGFR_cysC in follow-up at either year 3 or 10) or incident CKD (follow-up eGFR_cysC≤60 ml/min per 1.73 m² in individuals with baseline GFR>60 ml/min per 1.73 m²). Multivariable logistic regression models and Poisson regression models were used to evaluate the association with decline in KF and incident kidney disease, respectively. We also assessed for the independent associations among the exposure measures by including them in the same model.

Two-thousand four-hundred and eighty-nine individuals were included. Mean age was 74±3 years, 49% were men, 39% were black, 59% were hypertensive, and 15% were diabetic. KF decline occurred in 17% of the population, whereas incident CKD also occurred in 17% of those at risk. In continuous models, SAT, VAT, IMAT, BMI, and WC (per SD increase) were all significantly associated with KF decline. There was a significant interaction between VAT and CKD with regard to KF decline (P=0.01). Only VAT, BMI, and WC were associated with incident CKD. Only VAT remained a significant risk factor for incident CKD when other exposure variables were included in the same model. There was no association between any measure of obesity and kidney outcomes when creatinine values at years 3 and 10 were used to estimate changes in eGFR.

Anthropometric measures of body fat appear to provide as consistent estimates of KF decline risk as CT measures in elders.