Body Composition Has Limited Influence on the eGFRcys/eGFRcrea Ratio in Older Women
Rona Dawar, Anders Christensson, Kristina E Åkesson, Agne Laucyte-Cibulskiene, Linnea MalmgrenAbstract
Background
Kidney function is best estimated using both creatinine- and cystatin C–based eGFR. A low eGFRcys/eGFRcrea ratio (<0.7), termed selective glomerular hypofiltration syndromes (SGHS), is associated with increased cardiovascular risk. While differences in filtration for molecules with different molecular masses may explain this, non-renal factors such as body composition have also been proposed. We aimed to assess whether body composition determines the eGFRcys/eGFRcrea ratio in older women.
Methods
In 1044 women aged 75 from the OPRA cohort, followed to ages 80 (n = 715) and 85 (n = 382), we analyzed associations between the eGFRcys/eGFRcrea ratio and body composition (fat and appendicular lean mass), muscle strength (knee extension, Nm), and sarcopenia (EWGSOP2-criteria). Adjusted R² was reported from linear regression model assessing the eGFRcys/eGFRcrea ratio as the dependent variable adjusted for hsCRP, smoking, and steroid treatment.
Results
Associations between body composition measures and the eGFRcys/eGFRcrea ratio were generally low and attenuated with age. No significant association was observed between fat mass and the ratio at any age. Muscle mass was positively associated with the ratio at age 75 and 80, but not at age 85. Muscle strength was consistently associated with the eGFRcys/eGFRcrea ratio across all ages, although the proportion of explained variance declined with increasing age (adjusted R2 7.4%, 6.0% and 2.4% at ages 75, 80 and 85, respectively). Sarcopenia was inversely associated with the ratio at ages 75 and 85, but not at age 80.
Conclusion
Body composition, muscle strength, and sarcopenia showed only weak associations with the eGFRcys/eGFRcrea ratio in older women. These findings suggest that non-body composition factors, including intrinsic renal mechanisms such as selective filtration of larger molecules, may contribute to a low eGFRcys/eGFRcrea ratio.