Change of glomerular filtration rate in healthy adults with aging.

Aim: In order to determine the relationship between glomerular filtration rate (GFR) and age, the associated factors, and the accurate method of GFR in healthy adults, we conducted a cross-sectional study in community-dwelling adults in Beijing.

Methods: Renal function of 201 clinically healthy subjects was determined using technetium-99 m-labelled diethylene triamine pentacetic acid ((99m)Tc-DTPA). Estimated GFR was calculated with the Cockcroft-Gault (CG) equation, abbreviated Modification of Diet in Renal Disease (MDRD) equation, and plasma clearance of creatinine (Ccr). Serum cystatin C, biomarkers of inflammatory and endothelial cells were analyzed as well. Protein intake, carotid artery intima-media thickness and plaque formation were assayed as well.

Results: Glomerular filtration rate was negatively associated with age and the correlation coefficient for (99m)Tc-GFR, CG-GFR, MDRD-GFR, Ccr were -0.643, -0.736, -0.55 and -0.619, respectively (P < 0.001), while the correlation coefficient between cystatin C and age was 0.681 (P < 0.001). Estimated GFR were associated with measured GFR, and the correlation coefficient for Ccr, CG-GFR and MDRD-GFR were 0.813, 0.582 and 0.418, respectively (P < 0.001). The area under the receiver-operator curve of Ccr was larger, CG was smaller while MDRD was the smallest, and the difference was significant (P < 0.001). So a predicted equation was presented by cystatin C and C-reactive protein for the elderly.

Conclusion: In the clinically healthy adults, GFR declined with age. MDRD and CG equation are not suitable to estimate GFR in healthy adults. The predicted equation established by cystatin C and C-reactive protein may be more accurate.