Relationship of Frailty with Kidney Function in Adults More Than 60-Years-Old: Effect of Using Different Formulas to Estimate Glomerular Filtration Rate

OBJECTIVE: Determine the relationship of renal function with frailty using different formulas for estimated glomerular filtration rate (eGFR). METHODS: Individuals who were 60-years-old or more (n=507) were recruited from August 2020 to June 2021, and the FRAIL scale was used to classify them as non-frail or frail. The three equations used to compute the eGFR were based on serum creatinine (eGFRcr), cystatin C (eGFRcys), or SCr+CysC (eGFRcr-cys). Renal function was classified using eGFR and defined as normal (≥90 mL/min/1.73m(2)), mild damage (59–89 mL/min/1.73m(2)), or moderate damage (≤60 mL/min/1.73m(2)). The relationship of frailty with renal function was analyzed. A subset of participants (n=358) was used to analyze changes in eGFR from 1 January 2012 to 31 December 2021 according to frailty and using the different eGFR equations. RESULTS: There were significant differences between the eGFRcr-cys and eGFRcr values in the frail group (P<0.05), but not the non-frail group; however, the differences between the eGFRcr-cys and eGFRcys values were significant in the frail and non-frail groups (P<0.001). Based on each eGFR equation, the prevalence of frailty increased as eGFR decreased (P<0.001), but there was no significant relationship after adjusting for age or the age-adjusted Charlson co-morbidity index. There were temporal declines in eGFR in all three frailty groups (robust, pre-frail, and frail), especially in the frail group (2.226 mL/min/1.73m(2) per year; P<0.001). CONCLUSION: For older individuals who are frail, the eGFRcr value may not provide accurate estimates of renal function. Frailty is associated with a rapid decline in kidney function.