Rate of kidney function decline in older adults: a comparison using creatinine and cystatin C.

BACKGROUND/AIMS The aim of this study was to determine the decline in the estimated glomerular filtration rate (eGFR) in elderly persons and to compare estimates based on creatinine and cystatin C. METHODS In the Cardiovascular Health Study, GFR changes in an elderly cohort were estimated from serum creatinine and cystatin C measured at baseline, year 3 and year 7 in 4,380 participants (age 72 +/- 5 years at entry). Outcomes were mean eGFR decline, incident chronic kidney disease (CKD) and rapid decline in eGFR (annual loss >3 ml/min/1.73 m(2)). RESULTS Mean annual eGFR loss as estimated from creatinine was 0.4 +/- 3.6 ml/min/1.73 m(2), with 16% of the participants experiencing a rapid decline. Mean eGFR loss as estimated from cystatin C was 1.8 +/- 2.6, with 25% of the participants experiencing a rapid decline (p < 0.001 for both). Among participants without baseline CKD, incident CKD was detected at year 7 in 10% (n = 263) using creatinine and 19% (n = 544) using cystatin C (p < 0.001). Increasing age was the strongest predictor of rapid decline; adjusted odds ratios were 1.38 (1.16-1.65), 1.62 (1.31-1.99) and 2.96 (2.28-3.84) for participants aged 70-74, 75-79 and 80+ at baseline, compared with those aged 65-69. CONCLUSION In elderly persons, cystatin C estimated substantially larger declines in kidney function than creatinine did. Defining the optimal measurement of kidney function in elderly persons should be a high priority for future research.