Glomerular filtration rate variation with age in healthy normal adults

Abstract

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Objectives: Glomerular filtration rate (GFR) in normal adult population is commonly believed to decrease at a rate of 10mL/min per decade after the age of 30 based on inference from older radiopharmaceuticals and creatinine clearance estimates. As healthy mature renal transplant donors become available, GFR is a commonly used tool to assess for adequacy of renal function.

Methods: 282 healthy mixed race and gender adult potential renal transplant donors ranging in age from 20-70yrs were prospectively sent for GFR assessment by nuclear medicine techniques. GFR assessment was performed using Tc-DTPA blood sampling with samples obtained at 60 and 180 minutes. Data was normalized for standard body surface area of 1.73m^2, and analyzed by the same individuals in the same nuclear medicine hotlab. Parameters of age, sex, height and weight were also recorded as well as clinical and laboratory tests as required by the pre-renal transplant clinic. Regression analysis of GFR with age was performed.

Results: Linear regression analysis demonstrates GFR to decrease by 6 mL/min/1.73m^2 from the 3rd decade onward, with a significant regression F-stat (P<0.01). Residual plot analysis gives a wider distribution in the middle decades (40-60yrs) with segmental linear regression demonstrating improved correlation and significance using a near horizontal model for the first 2(n=88), and the last decade(n=41)analyzed, with maximal decrease in GFR present between the ages of 40-60 (n=153).

Conclusions: GFR assessed by nuclear medicine blood sampling techniques appears to decrease with age at an overall rate lower than commonly believed. Regression analysis demonstrates GFR to vary more widely and decrease most rapidly in the 40-60yr bracket, with the overall shape of GFR change with age appearing sigmoidal. In healthy mature adults (>60yrs), the GFR appears to decrease less rapidly than during the middle decades, implying more mature adults meet the criteria for renal transplant donors.