How much does eGFR go down with age? An expert guide

Studies indicate that for healthy individuals, a gradual and natural decline in kidney function begins after the age of 30 or 40. Understanding how much eGFR goes down with age is essential for interpreting lab results and maintaining optimal senior health.

Quick Summary

The average eGFR decreases by approximately 1 mL/min/1.73 m² per year after age 40, though individual rates vary based on overall health, lifestyle, and other factors.

Key Points

• Expected Decline: eGFR typically falls by about 1 mL/min per year after age 40 due to natural aging.

• Normal Varies by Age: What's considered a healthy eGFR value decreases with age; average ranges differ significantly for seniors compared to young adults.

• Not Always CKD: A lower eGFR in older age doesn't automatically mean chronic kidney disease, but it warrants medical evaluation to rule out other causes.

• Lifestyle Matters: Modifiable factors like diet, exercise, and blood pressure control can help slow kidney function decline.

• Monitor Over Time: Small, isolated fluctuations in eGFR are normal; focus on the long-term trend rather than a single number.

• Consult a Doctor: If your eGFR falls consistently below 60, consult a doctor to create a proper management plan.

The Expected Rate of eGFR Decline with Aging

The kidneys, like all organs, undergo changes with age that lead to a physiological reduction in function. Numerous studies confirm that the estimated glomerular filtration rate (eGFR) in healthy individuals typically begins to decrease during mid-adulthood. The median rate of this decline is approximately 1 mL/min/1.73 m² per year. This means that over a decade, a healthy person can expect their eGFR to be about 10 points lower than it was previously.

It's important to remember that this is an average. The rate of decline can differ significantly among individuals based on genetics, lifestyle, and the presence of other health conditions. For example, some people experience little to no age-related decline, while others see a more rapid drop.

What is a "Normal" eGFR for Your Age?

Because eGFR naturally declines with age, what is considered "normal" for a young adult is different from what's considered typical for a senior. Healthcare providers interpret results in the context of a person's age. The National Kidney Foundation provides average eGFR ranges for different age groups, which can serve as a general guide:

Age (years)	Average eGFR (mL/min/1.73m²)
20–29	116
30–39	107
40–49	99
50–59	93
60–69	85
70+	75

It is crucial to note that an eGFR below 60 mL/min/1.73m² for three months or longer is a criterion for diagnosing chronic kidney disease (CKD), regardless of age. However, the median eGFR for a person over 70 is 75, well above this threshold. This highlights why a doctor's medical evaluation is essential to determine if a lower eGFR is a normal age-related change or a sign of disease.

Normal Aging vs. Chronic Kidney Disease

The physiological decline of eGFR with age can sometimes lead to an overdiagnosis of CKD in older adults. The diagnostic criteria for CKD can label many healthy seniors as having kidney disease simply because their GFR has decreased with time. For this reason, new guidelines sometimes consider age-adapted thresholds. The key is differentiating between the natural loss of nephrons and damage caused by other conditions. A low eGFR in a senior without other signs of kidney damage, like proteinuria (protein in the urine), may be managed differently than in a younger person.

Factors That Accelerate Kidney Function Decline

While some eGFR decline is expected, several factors can accelerate this process, potentially leading to more significant kidney problems:

• High Blood Pressure (Hypertension): Uncontrolled high blood pressure is a major risk factor for kidney disease and can significantly hasten the decline in eGFR.
• Diabetes: High blood sugar levels can damage the kidneys over time, and both type 1 and type 2 diabetes are leading causes of kidney failure.
• Smoking: Tobacco use damages blood vessels and reduces blood flow to the kidneys, speeding up the decline in function.
• Obesity: Being overweight or obese places extra strain on the kidneys, increasing the risk of chronic kidney disease.
• Inflammation: Chronic inflammation, often linked to other conditions, can contribute to kidney damage and accelerated eGFR decline.
• Certain Medications: Long-term use of certain medications, including some non-steroidal anti-inflammatory drugs (NSAIDs), can harm the kidneys.

The Difference Between eGFR and Measured GFR

To understand your eGFR fully, it helps to know how it is determined and how it differs from a measured GFR (mGFR). Most eGFR results are calculated using blood creatinine levels, along with age, sex, and race.

Feature	Estimated GFR (eGFR)	Measured GFR (mGFR)
Method	Calculated using a formula based on blood creatinine and demographic factors.	Directly measured in a lab using injected filtration markers, like iohexol.
Availability	Widely accessible and used for routine screening.	More complex, time-consuming, and typically reserved for specific clinical settings.
Accuracy	Can be less precise, especially in older adults with reduced muscle mass, as creatinine levels can be misleading.	Considered the gold standard and most accurate assessment of kidney function.
Primary Use	Monitoring trends and for initial detection of kidney dysfunction.	Confirming a CKD diagnosis or for research purposes.

Some eGFR formulas also incorporate serum cystatin C, a different protein, which can provide a more accurate estimate in some cases, especially in the elderly where creatinine levels may be low due to muscle wasting.

Actionable Steps to Protect Your Aging Kidneys

While you can't stop the natural aging process, you can take proactive steps to slow the decline of your kidney function and support overall kidney health:

1. Manage Blood Pressure and Diabetes: Work with your doctor to keep your blood pressure and blood sugar levels within a healthy range. Medications like ACE inhibitors or ARBs can be particularly protective for the kidneys.
2. Stay Hydrated: Drinking enough water helps your kidneys flush out toxins and waste products. However, always follow your doctor’s advice, especially if you have been diagnosed with kidney disease.
3. Adopt a Kidney-Friendly Diet: Reduce your intake of processed foods high in sodium, sugar, and unhealthy fats. Increase consumption of fresh fruits, vegetables, and whole grains. Limiting animal protein can also reduce the workload on your kidneys.
4. Exercise Regularly: Engaging in moderate physical activity can help control blood pressure and blood sugar, both of which are beneficial for kidney health.
5. Maintain a Healthy Weight: Losing weight if you are overweight or obese reduces the strain on your kidneys and other organs.
6. Avoid Harmful Habits: Quit smoking and limit alcohol intake, as both can have a negative impact on kidney function.
7. Medication Awareness: Always discuss any medications, including over-the-counter drugs and supplements, with your doctor, as some can harm the kidneys, especially in older adults.

Conclusion: Interpreting Your eGFR Results

The rate at which eGFR goes down with age is a complex but natural process. For most healthy adults over 40, this decline averages about 1 mL/min per year. What's considered a typical eGFR changes as we age, so a lower number in a senior is not always cause for alarm. The key is to monitor the trend of your eGFR over time rather than focusing on a single, isolated lab result, which can fluctuate. By adopting a healthy lifestyle and working closely with your healthcare provider to manage other conditions, you can effectively slow the decline of your kidney function and support healthy aging. For additional authoritative information, consider visiting the National Kidney Foundation.

Frequently Asked Questions

What is eGFR?

eGFR stands for estimated Glomerular Filtration Rate. It is a calculated measure of how well your kidneys are filtering waste from your blood, based on a simple blood test that typically measures serum creatinine levels.

Why does eGFR decrease as we get older?

The decline is a natural part of the aging process, also known as senescence. It is associated with the progressive loss of nephrons (the filtering units of the kidney) over time, and is often independent of underlying disease.

Is a low eGFR in a senior always a sign of kidney disease?

Not necessarily. While a consistently low eGFR can indicate chronic kidney disease, it can also reflect the normal, physiological aging of the kidneys. Doctors must consider other factors, like protein in the urine, to make a definitive diagnosis.

What should I do if my eGFR is below 60?

If your eGFR is below 60 for three months or more, it is considered chronic kidney disease (CKD). You should work with your healthcare provider to manage the condition and slow its progression.

Can I improve my eGFR?

While it is unlikely that eGFR will ever return to the levels of a younger person, adopting healthy habits can help slow the rate of decline and improve overall kidney health. These include managing blood pressure and diabetes, exercising, and eating a kidney-friendly diet.

Does exercise affect eGFR?

Yes, regular, moderate-intensity exercise can be beneficial. Studies have shown that physical activity may help slow the rate of kidney function decline, especially in older adults.

How do my doctors know if the eGFR decline is normal or pathological?

Your doctor will consider the rate of decline over time, your overall health, the presence of comorbidities like hypertension or diabetes, and additional lab results, such as a urine test for albuminuria (protein in the urine), to make a comprehensive assessment.