What is the rate of decline of Glomerular Filtration Rate (GFR) with aging?

From the Guidelines

Glomerular filtration rate (GFR) typically declines at a rate of about 1 to 2 mL/min per year after the sixth decade of life, as stated in the seventh report of the joint national committee on prevention, detection, evaluation, and treatment of high blood pressure 1. This decline is considered a normal part of aging and varies among individuals based on factors such as genetics, underlying health conditions, and lifestyle choices. The average GFR for a young adult is approximately 120-130 mL/min/1.73m², which means by age 80, many healthy individuals may have a GFR around 70-80 mL/min/1.73m². This age-related decline occurs due to structural changes in the kidneys, including loss of nephrons (the kidney's filtering units), glomerulosclerosis (scarring of the glomeruli), and reduced renal blood flow. It's essential to note that while some GFR decline is expected with aging, accelerated decline may indicate kidney disease and should be evaluated. Regular monitoring of kidney function becomes increasingly important with age, especially for those with risk factors like diabetes, hypertension, or family history of kidney disease. Maintaining healthy blood pressure, controlling blood sugar, staying hydrated, avoiding nephrotoxic medications, and following a kidney-friendly diet can help minimize the rate of GFR decline as you age, as suggested by the national kidney foundation practice guidelines for chronic kidney disease: evaluation, classification, and stratification 1. Some key points to consider include:

• The age-related decline in GFR has been considered part of normal aging, but decreased GFR in the elderly is an independent predictor of adverse outcomes, such as death and cardiovascular disease (CVD) 1.
• The definition of chronic kidney disease is the same, regardless of age, and the prevalence of chronic kidney disease increases with age; approximately 17% of persons older than 60 years of age have an estimated GFR less than 60 mL/min per 1.73 m2 1.
• The guidelines define kidney failure as either GFR less than 15 mL/min per 1.73 m2, which is accompanied in most cases by signs and symptoms of uremia, or a need to start kidney replacement therapy (dialysis or transplantation) 1. However, the most critical consideration is the rate of decline, which can be influenced by various factors, including blood pressure control, as highlighted in the seventh report of the joint national committee on prevention, detection, evaluation, and treatment of high blood pressure 1.

From the Research

Decline of Glomerular Filtration Rate (GFR) with Age

• The decline of GFR with age is a progressive process that starts after the age of 30 and continues to decline steadily after the age of 60 2.
• Studies have shown that the rate of decline may accelerate after age 50-60 years 3.
• The decline of GFR with age is associated with structural changes in the kidneys and is a part of the normal physiologic process of cellular and organ senescence 3.

Rate of Decline

• The estimated 1-year slope for ages 75 and 90 diminished for men from -1.67 to -0.99 and for women from -1.52 to -0.97 4.
• The decline of GFR is nonlinear, with a decreasing rate of decline with increasing age in older adults 4.
• Multivariable adjustment attenuated slopes only minimally, suggesting that the decline of GFR is largely independent of other factors 4.

Comparison of Equations

• Different equations for estimating GFR, such as the MDRD and MAYO equations, produce different profiles of evolution of GFR with age 2.
• The MDRD equation produces a faster decrease in early adulthood and a flatter curve after the age of 60, while the MAYO equation produces a more linear effect 2.
• Equations including cystatin C demonstrate a nonlinear slope, challenging the previously assumed linearity of the decline of eGFR in old age 4.

Clinical Implications

• The decline of GFR with age should be taken into account when evaluating eGFR in clinical practice 2, 3.
• A single cut-off value of GFR normality for all ages may lead to underdiagnosis of young adults and overdiagnosis of elderly individuals 2.
• Guidelines should consider the observed reduction of kidney function with age in the normal population for optimal evaluation of eGFR 2.