Although a significant decrease in MMSE values across CKD stages has been reported in frail patients [13], in the Cardiovascular Health Study, in which cognitive function was assessed by the Modified MMSE and DSST, no significant differences were detected between participants with cystatin C-based eGFR ≥ 90 mL/min/1.73 m2 and those with eGFR of 60 to below 90 mL/min/1.73 m2 at baseline [30]. This evidence concerns the gene CST4 and chronic kidney disease.