The Importance of GFR for Kidney Function
The glomerular filtration rate, or GFR, is the best overall measure of kidney function. It estimates how well your kidneys are filtering waste products from your blood. Your kidneys have tiny filters called glomeruli that are essential for this process. Knowing your GFR helps healthcare professionals detect potential kidney problems early, allowing for timely intervention and management. While a GFR over 90 mL/min/1.73 m² is typically considered normal for young, healthy adults, this benchmark changes with each decade of life.
Age-Related Decline: What to Expect
It is well-established that GFR declines with age, even in healthy individuals. This is a natural physiological process, and what is considered a normal GFR range shifts downward as you get older. Several studies, including the prominent Gutenberg Health Study and research on healthy kidney donors, have confirmed this trend.
Average eGFR by Age Group
To illustrate the typical age-related decline, the National Kidney Foundation provides a reference for average estimated GFR (eGFR) values.
| Age (years) | Average eGFR (mL/min/1.73 m²) |
|---|---|
| 20–29 | 116 |
| 30–39 | 107 |
| 40–49 | 99 |
| 50–59 | 93 |
| 60–69 | 85 |
| 70+ | 75 |
It is important to remember that these are average values, and a person's individual result can vary. A key takeaway is that an eGFR of 75 in a 75-year-old may be within the expected range for their age, whereas the same reading in a 35-year-old could indicate early kidney disease and warrant further investigation.
Interpreting Your GFR Results
Medical guidelines classify chronic kidney disease (CKD) into stages based on GFR levels. The standard threshold is a GFR below 60 mL/min/1.73 m² for three or more months, which is considered a sign of CKD. However, the age-related decline complicates this rigid cutoff, especially for older adults. Some have argued that using a single, fixed threshold may lead to the overdiagnosis of CKD in the elderly population.
The Role of Your Healthcare Provider
Your doctor will interpret your GFR result by considering several factors in addition to your age. These include:
- Your overall health and medical history, especially conditions like diabetes and high blood pressure, which affect kidney function.
- Additional blood and urine tests, such as creatinine, blood urea nitrogen (BUN), and urine albumin, to provide a more complete picture of your kidney health.
- Other personal characteristics, including your gender, weight, and muscle mass.
Beyond the Numbers: Maintaining Kidney Health
Knowing your GFR is the first step, but proactive management is key for seniors. While some decline is inevitable, lifestyle choices can help maintain kidney function as you age. Your doctor may recommend:
- Dietary adjustments: A diet low in salt and processed foods can reduce the burden on your kidneys. For some, a low-meat or vegetarian diet may be advised, as excessive protein intake can impact kidney function.
- Managing underlying conditions: For those with diabetes or hypertension, diligent management is critical. Poorly controlled blood sugar and blood pressure can accelerate the loss of kidney function.
- Medication review: Some medications can affect kidney function. It's vital to regularly review all prescriptions, over-the-counter drugs, and supplements with your doctor.
- Staying hydrated: Proper hydration is always important for kidney health, though special attention may be needed for older adults whose thirst response can decrease.
For more detailed information on kidney health and aging, the National Institutes of Health (NIH) is an excellent resource [https://www.nih.gov/health-information/nih-senior-health/kidney-health].
When to Take Your GFR Seriously
While a GFR below 90 is normal as you age, a sudden, rapid, or significant drop in GFR is always a cause for concern. You should discuss any GFR reading below 60 mL/min/1.73 m² with your doctor, even if you are older. This is because even an age-related decline can increase your risk for complications. Early detection is the best defense against advanced kidney disease and related health issues, such as cardiovascular problems.
Your healthcare provider is your best partner in interpreting what your GFR means for your unique situation. They can help you create a personalized plan to maintain your kidney function for years to come.
