Is it normal for eGFR to decrease with age?

Studies consistently show that kidney function, measured by estimated Glomerular Filtration Rate (eGFR), naturally declines with age. This phenomenon, often termed renal senescence, is a normal physiological process that occurs in all individuals, including those in good health. So, is it normal for eGFR to decrease with age? Yes, to a certain extent, but the rate and factors involved are critical to understand.

Quick Summary

Yes, it is normal for eGFR to gradually decrease with age, a process known as renal senescence, which reflects the natural decline in kidney function over time. While this slow, expected reduction is common, a rapid or significant drop can indicate an underlying health issue and warrants a medical evaluation.

Key Points

• Normal Decline: A gradual decrease in eGFR is a normal, physiological part of healthy aging, often beginning in adulthood.

• Rate of Decline: The average, expected decline in eGFR is approximately 1 mL/min/1.73 m² per year in healthy individuals.

• Rapid Drop Warning: A sudden or accelerated decline in eGFR is not normal and may indicate an underlying health problem, requiring further medical investigation.

• Age vs. Disease: It is important to distinguish between normal age-related renal senescence and a decline caused by chronic kidney disease (CKD) or other illnesses.

• Risk Factors: Conditions like hypertension, diabetes, and cardiovascular disease can speed up the rate of eGFR decline.

• Accurate Assessment: In older adults, creatinine-based eGFR can be misleading due to lower muscle mass; confirmatory testing using cystatin C (eGFRcys) can provide a more accurate reading.

Understanding Estimated Glomerular Filtration Rate (eGFR)

Estimated Glomerular Filtration Rate, or eGFR, is a crucial metric used to assess kidney function. It's calculated using a blood test that measures creatinine, a waste product from muscle metabolism. The eGFR formula combines your creatinine level with other factors, such as age, sex, and body size, to provide an estimate of how well your kidneys are filtering waste from your blood. A normal eGFR for a healthy adult is typically over 90 mL/min/1.73 m². However, this number is an estimate, and a range of factors can influence it.

The Physiological Decline of eGFR

The age-related decrease in eGFR is a well-documented biological process. Starting around age 30 to 40, kidney function begins to decline, and this rate may accelerate after age 50 to 60. This is part of the natural aging process, as the number of functioning nephrons, the tiny filtering units in the kidneys, decreases over time.

Research indicates that for many healthy individuals, the average annual decline is approximately 1 mL/min/1.73 m² per year. It's important to distinguish this gradual, expected decline from a rapid drop, which can be a sign of a more serious issue.

Normal Aging vs. Chronic Kidney Disease

While a slow, steady decrease in eGFR is expected with age, it's not always a cause for concern. For many older adults, a lower eGFR is simply a sign of normal, healthy aging. However, the line between physiological decline and the development of chronic kidney disease (CKD) can be blurry, and it is a point of debate among medical professionals.

A diagnosis of CKD is typically made when eGFR falls below 60 mL/min/1.73 m² for three or more months. In older adults, a low eGFR might trigger a CKD diagnosis, even if they have no other symptoms. This has led to proposals for age-adapted eGFR thresholds to avoid 'over-diagnosing' CKD in the elderly population.

How Coexisting Conditions Impact eGFR Decline

The rate of eGFR decline is often influenced by other health conditions, not just age. Several factors can accelerate the loss of kidney function, including:

• Hypertension (High Blood Pressure): Uncontrolled high blood pressure is a leading cause of kidney damage. A systematic review found that individuals with hypertension experience a significantly faster rate of eGFR decline.
• Diabetes: Poorly controlled diabetes can lead to kidney damage and a faster decline in eGFR. Initially, diabetes can cause hyperfiltration, a state where kidneys work overtime, but this eventually leads to accelerated decline.
• Cardiovascular Disease: Impaired heart function can negatively impact blood flow to the kidneys, leading to a quicker drop in eGFR.
• Smoking: Tobacco use is another modifiable risk factor associated with a more rapid decline in kidney function.

Tools for Accurate Assessment

To get a more precise picture of kidney function, particularly in older adults, doctors may use more sophisticated tools and markers than just a single creatinine-based eGFR reading. This is because creatinine levels can be misleading in the elderly due to reduced muscle mass, which naturally occurs with age.

Creatinine vs. Cystatin C

For a more accurate assessment, especially when eGFR is in the borderline range (45-74 mL/min/1.73 m²), confirmatory testing using cystatin C (eGFRcys) may be recommended. Cystatin C is a protein produced by all cells in the body, and its levels are less affected by muscle mass, making it a more reliable marker in older or frail individuals. Combining both creatinine and cystatin C measurements (eGFRcr-cys) provides the most accurate estimation of GFR.

Lifestyle and Management Strategies

Regardless of whether an eGFR decline is related to age or disease, proactive management can help preserve kidney health. Focusing on overall wellness, rather than just the number, is key.

Comparison of eGFR Influences	Factor	Impact on eGFR Decline	Management Strategy
Age	Gradual, physiological decline (renal senescence).	Maintain a healthy lifestyle, monitor regularly.
High Blood Pressure	Can significantly accelerate the rate of decline.	Control blood pressure through diet, exercise, and medication as prescribed by a doctor.
Diabetes	Increases risk of kidney damage and faster decline.	Strict management of blood glucose levels is crucial.
Cardiovascular Disease	Impaired heart function negatively impacts kidney blood flow.	Manage heart health, exercise regularly, follow a heart-healthy diet.
Medications	Some medications can be hard on the kidneys and affect eGFR.	Regular review of medications with a healthcare provider is important.
Hydration	Dehydration can temporarily lower eGFR.	Stay well-hydrated throughout the day.

Staying Proactive with Kidney Health

For seniors and their caregivers, being proactive about kidney health means understanding these nuances. It's crucial to have open conversations with a healthcare provider about eGFR trends, not just isolated readings. Regular monitoring allows doctors to identify if a decline is within the expected range for your age or if further investigation is needed.

Medical guidelines and standards for defining and managing chronic kidney disease in older populations are continually evolving. One authority that provides comprehensive guidelines on kidney disease is the National Kidney Foundation. Their resources can provide valuable information for both patients and healthcare providers.

In conclusion, a slow decrease in eGFR as one gets older is a normal part of the aging process. However, this does not mean it should be ignored. It serves as a reminder to prioritize a healthy lifestyle and regular medical monitoring, especially for those with coexisting conditions. A collaborative approach with your doctor can help you understand your eGFR trend and take appropriate action to protect your kidney health for the long term.

Frequently Asked Questions

What is a normal eGFR level for an older person?

There is no single 'normal' number for everyone. Because eGFR naturally declines with age, a value considered normal for a 30-year-old would be different for a 70-year-old. Doctors typically look at the trend over time rather than a single reading. A persistent eGFR below 60 mL/min/1.73 m² is a criterion for Chronic Kidney Disease (CKD) but must be evaluated in the context of other health factors.

Can I improve my eGFR after a decrease with age?

While it's unlikely to reverse the natural, age-related decline, you can often slow down further decreases. Focusing on healthy habits like managing blood pressure, controlling blood sugar, exercising, and maintaining a healthy diet can support overall kidney health.

How can I tell if my eGFR decrease is normal or from kidney disease?

The key is the rate and magnitude of the change. A gradual, slow decline over many years is more typical of normal aging. A rapid or sudden drop, or a decline accompanied by other symptoms, is more concerning. A healthcare provider can analyze your eGFR trends and other health markers to determine the cause.

Do medications affect eGFR readings in older adults?

Yes, many medications can affect kidney function and eGFR, both temporarily and long-term. It's important to have a regular review of all your medications with your healthcare provider to ensure they are not negatively impacting your kidneys. Staying well-hydrated is also crucial, as dehydration can affect readings.

Why is eGFR sometimes less accurate in older individuals?

eGFR is often calculated using serum creatinine, a byproduct of muscle. As people age, muscle mass typically decreases, leading to lower creatinine production. This can cause the eGFR formula to overestimate kidney function, especially in the elderly or frail.

What is cystatin C, and why is it sometimes used instead of creatinine?

Cystatin C is another marker for kidney function. Unlike creatinine, its levels are less influenced by muscle mass, making it a more accurate measure of GFR in certain populations, including older adults. Doctors may use a combined eGFRcr-cys measurement for the most precise results.

Should I be concerned about a mild eGFR decrease if I feel healthy?

A mild, gradual decrease in eGFR as you age is common and not necessarily a cause for alarm if you are otherwise healthy. However, it's a good reminder to maintain a kidney-healthy lifestyle and discuss your eGFR trends with your doctor during routine checkups.