Sex- and age-specific associations between body composition markers and estimated glomerular filtration rate-results of a population-based study.

Background: Recent studies have indicated that body composition may affect kidney function. The aim of this study was to examine the sex- and age-related association between body composition markers and the estimated glomerular filtration rate (eGFR). Methods: Analyses were based on data from the population-based 'Study of Health in Pomerania' (SHIP), including data from 4211 individuals enrolled in the SHIP Trend-0 cohort. Body composition markers included measurements from classic anthropometry (body mass index, waist-to-hip ratio), body impedance analysis and magnetic resonance imaging (subcutaneous, hepatic and visceral fat mass). The eGFR was estimated using creatinine- and Cystatin C-based formulas. Cross-sectional analysis was performed using linear regression models adjusted for confounding variables. Results: Generally, higher values of body composition markers were associated with lower eGFR levels for all formulas, while higher relative fat-free mass was associated with higher eGFR. The effects were more pronounced in women compared to men. Regarding age dependency, increased values of body or fat mass were associated with higher eGFR in younger age groups, but with lower eGFR in older age groups. In contrast, higher relative fat-free mass was associated with increased eGFR in older age groups. Conclusions: Increased body and fat mass, regardless of distribution, and a lower percentage of muscle mass are associated with lower eGFR especially in women and older individuals.