The natural decline of eGFR
As people age, their kidneys undergo natural changes that can affect their filtering ability. The kidneys are composed of millions of tiny filtering units called nephrons. As a person gets older, some of these nephrons can be lost, and the remaining ones may not function as efficiently. This leads to a gradual, progressive reduction in the overall rate of glomerular filtration, which is what the eGFR measures.
This physiological decline typically begins in early adulthood, around age 30 to 40, and continues throughout a person's life. Studies have shown that for a healthy adult without other health conditions, this decline is gradual, often less than 1.07 mL/min/1.73 m² per year. For this reason, a lower eGFR reading in an older adult should be interpreted differently than the same reading in a younger individual. A result below 60 mL/min/1.73 m² may be a flag for chronic kidney disease (CKD) in younger people, but it may be considered a normal finding in some older individuals.
Factors influencing the rate of eGFR decline
While a decline in eGFR with age is normal, several other factors can influence the rate and severity of this decrease. These factors can accelerate kidney function decline, turning a normal aging process into a more significant health concern. Some of these include:
- Chronic Diseases: Conditions like hypertension (high blood pressure) and diabetes are among the most significant risk factors for accelerating kidney function decline and progression to CKD.
- Lifestyle Choices: Unhealthy habits such as smoking, poor diet, excessive alcohol consumption, and physical inactivity can all contribute to reduced kidney health over time.
- Medications: Certain medications, including some over-the-counter pain relievers (NSAIDs) and other prescription drugs, can affect kidney function, especially with long-term use.
- Genetics: An individual's genetic predisposition and family history of kidney disease can play a significant role in their long-term kidney health.
Interpreting eGFR results in older adults
When a healthcare provider evaluates an older adult's eGFR, they don't just look at the number in isolation. They consider the full clinical picture, including the patient's age, overall health, and the presence of other conditions. Here's what this interpretation involves:
- Context is Key: A moderately low eGFR reading in a healthy older adult may simply reflect the normal aging process, not a disease state. For example, a 75-year-old with an eGFR of 55 may not be cause for alarm, whereas the same reading in a 40-year-old would warrant further investigation.
- Confirming with Other Tests: eGFR is an estimation, often calculated using serum creatinine, which can be influenced by muscle mass, age, sex, and race. For a more accurate assessment, especially in older adults, providers may order a confirmatory test using cystatin C, a protein less affected by muscle mass.
- Trend Monitoring: Tracking eGFR over time is more informative than a single measurement. A stable, low-normal eGFR is less concerning than a rapid, sudden drop, which suggests an acute kidney issue.
- Assessing Risk: The presence of other indicators, such as protein in the urine (albuminuria), provides crucial context. Albuminuria alongside a low eGFR is a strong sign of kidney damage, even if the eGFR number isn't below the standard threshold for CKD.
Comparison of age-related vs. disease-related eGFR decline
| Feature | Age-Related Decline | Disease-Related Decline (e.g., CKD) |
|---|---|---|
| Onset | Gradual, starting in early adulthood | Can be gradual or sudden, depending on the cause |
| Rate | Slow, predictable rate (approx. 1 mL/min/year) | Often faster and more significant |
| Associated Signs | Typically no other symptoms; may lack albuminuria | Often accompanied by other symptoms, such as fatigue, swelling, and changes in urination |
| Underlying Cause | Loss of nephrons and general kidney senescence | Damage to kidney structures from conditions like diabetes, hypertension, or inflammation |
| Reversibility | Not reversible; a natural part of aging | Progression can often be slowed or managed with treatment; may not be reversible |
Strategies for maintaining kidney health as you age
Even though eGFR naturally decreases with age, there are several steps older adults can take to support their kidney function and slow down any potential decline.
- Manage Underlying Conditions: Diligently control blood pressure and blood sugar levels if you have hypertension or diabetes. This is the single most effective strategy for protecting kidney function.
- Stay Hydrated: Drinking plenty of water helps the kidneys filter waste from the blood effectively.
- Eat a Healthy Diet: Follow a balanced diet, such as the DASH or Mediterranean diet, which are low in sodium and processed foods and rich in fruits, vegetables, and whole grains.
- Exercise Regularly: Moderate physical activity helps control weight and blood pressure, both of which support kidney health.
- Limit Certain Medications: Consult your doctor about avoiding or limiting the use of NSAIDs like ibuprofen, especially if you already have reduced kidney function. Always take medications as prescribed.
- Regular Check-ups: Schedule routine check-ups and screenings with your healthcare provider to monitor your kidney function over time, especially after age 60.
The importance of proactive management
Understanding that a decline in eGFR is a normal part of aging is empowering. It helps shift the focus from worrying about a specific number to adopting proactive health strategies. Instead of solely focusing on an eGFR value, a personalized approach to kidney health, including managing underlying risk factors, monitoring trends over time, and adopting a healthy lifestyle, is far more beneficial. For guidance on interpreting your specific results and creating a personalized plan for kidney wellness, always consult a healthcare professional, especially a nephrologist or your primary care physician.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Consult with a qualified healthcare professional for personalized medical guidance.
