Nonlinear Associations between Glomerular Function and Frailty: A National Study Comparing Glomerular Function Using...

Area of Science:

• Gerontology
• Nephrology
• Public Health

Background:

• Frailty and chronic kidney disease (CKD) are prevalent in aging populations.
• The relationship between kidney function and frailty is not fully understood, especially with different estimated glomerular filtration rate (eGFR) equations.

Purpose of the Study:

• To investigate the association between kidney function, estimated by various eGFR equations, and frailty in middle-aged and older Chinese adults.
• To compare the performance of creatinine-based (eGFRcr), cystatin C-based (eGFRcys), and combined (eGFRcr-cys) eGFR equations in predicting frailty.

Main Methods:

• Analysis of 17,864 participants (≥45 years) from the China Health and Retirement Longitudinal Study (CHARLS).
• Frailty assessed using the frailty index (FI) and Fried physical frailty phenotype.
• Kidney function estimated using CKD-EPI creatinine, cystatin C, and combined equations.
• Logistic regression, splines, and threshold models used to analyze associations.

Main Results:

• Lower eGFR was independently associated with higher frailty odds across all equations.
• eGFRcys showed the strongest and most consistent association with frailty, with significant associations at earlier stages of kidney dysfunction.
• Non-linear relationships were observed for eGFRcys and eGFRcr-cys, with inflection points indicating increased frailty risk.

Conclusions:

• Cystatin C-based eGFR is a more sensitive marker for frailty than creatinine-based estimates in this population.
• Integrating eGFRcys into kidney function assessment may improve the identification of individuals at risk for frailty.
• Further longitudinal and interventional studies are needed to confirm these findings.