Increased fat mass index is associated with decreased glomerular filtration rate estimated from cystatin C. Data from Malmö Diet and Cancer cohort

BACKGROUND: This study aims to describe associations of obesity and CKD in a Swedish urban population. The impact of fat mass, from bioimpedance analysis, on eGFR based on cystatin C and/or creatinine is studied. METHODS: 5049 participants from Malmö Diet and Cancer Study the cardiovascular arm (MDCS‐CV) with available body mass composition (single frequency bioimpedance analysis) and cystatin C measured at baseline were selected. Body mass index (kg/m(2)) was used to define overweight/obesity. eGFR was calculated using cystatin C (eGFR(CYS)) and creatinine (eGFR(CR)) equations: Chronic Kidney Disease Epidemiology Collaboration 2012 (CKD-EPI(CR,) CKD-EPI(CYS), CKD-EPI(CR-CYS))(,) eGFR(CYS) based on Caucasian, Asian, pediatric, and adult cohorts (CAPA), the Lund-Malmö revised equation (LMrev), and Modified Full Age Spectrum creatinine-based equation (EKFC(CR)). Two different fat mass index (FMI) z-scores were calculated: FMI z-score(Larsson) and FMI z-score(Lee). RESULTS: Lower eGFR(CYS) and eGFR(CR-CYS) following multiple adjustments were prevalent in overweight/obese subjects. Increase in FMI z-score(Larsson) or FMI z-score(Lee) was related to decrease in predicted CAPA, CKD-EPI(CYS), CKD-EPI(CR-CYS) and CAPA-LMrev equation. CONCLUSION: eGFR(CYS), in contrast to combined eGFR(CR-CYS) and eGFR(CR), demonstrate the strongest association between FMI and kidney function.