Understanding Average Kidney Function in Older Adults
For a 70-year-old, the concept of “average” kidney function is different than for a younger person. The kidneys naturally and gradually lose some of their filtering capacity over time, a process called renal senescence. This means that while an eGFR above 90 is considered normal for a young adult, a lower number is expected and often considered normal for a senior. However, this age-related change must be differentiated from more serious chronic kidney disease (CKD).
The primary measure of kidney function is the glomerular filtration rate (GFR). This measures how well the kidneys filter blood. A doctor will typically estimate this using blood tests for creatinine, and sometimes cystatin C, along with other factors like age, gender, and weight. The result is the estimated GFR (eGFR), which is a crucial indicator of kidney health.
Normal eGFR and Creatinine Levels at Age 70
The most cited figures suggest that a healthy 70-year-old typically has an average eGFR around 75 mL/min/1.73 m². This is lower than the average for someone in their 40s or 50s, but it's often not a cause for concern unless other signs of kidney damage, like protein in the urine, are present. Some studies even report that a significant portion of older adults have an eGFR below 60 mL/min/1.73 m² without having progressive disease.
Creatinine levels, a byproduct of muscle metabolism, are also used to assess kidney function. Because muscle mass decreases with age, an older person's creatinine level may not be as reliable as a standalone measure of kidney function. This is why calculating the eGFR, which includes age and gender, is so important. Normal serum creatinine ranges for adults are between 0.74 to 1.35 mg/dL for men and 0.59 to 1.04 mg/dL for women, but these can vary by laboratory.
Factors Influencing Kidney Function in Older Adults
While a decline in eGFR is expected with age, several risk factors can accelerate this process and lead to chronic kidney disease.
- Diabetes: High blood sugar can damage the tiny filtering units in the kidneys over time.
- High Blood Pressure (Hypertension): Uncontrolled high blood pressure is a leading cause of kidney damage.
- Cardiovascular Disease: Heart disease and heart failure significantly increase the risk of kidney problems.
- Obesity: Excessive weight puts added strain on the kidneys and is linked to a higher risk of CKD.
- Medications: Prolonged or excessive use of certain over-the-counter pain relievers, like NSAIDs (ibuprofen, naproxen), can damage the kidneys.
- Dehydration: Older adults are more susceptible to dehydration, which can put acute stress on the kidneys.
- Family History: A family history of kidney failure is a significant risk factor.
How to Protect and Maintain Kidney Function
Even with the natural aging process, seniors can take proactive steps to maintain their kidney health.
- Stay Hydrated: Drink plenty of water throughout the day. Older adults may have a reduced sense of thirst, so it's important to be mindful of fluid intake.
- Manage Underlying Conditions: Strictly controlling conditions like diabetes and high blood pressure is critical for preventing further kidney damage.
- Adopt a Kidney-Friendly Diet: A low-sodium diet rich in fruits, vegetables, and whole grains can be very beneficial. Limiting processed foods is key.
- Exercise Regularly: Consistent physical activity helps manage weight and blood pressure, both of which support kidney function.
- Avoid NSAID Overuse: Use caution with medications like ibuprofen and naproxen, which can be hard on the kidneys, especially over the long term.
- Get Regular Check-ups: Annual screenings for kidney function, including blood and urine tests, are recommended, especially for those over 60 or with risk factors.
The Importance of Regular Screening
Early kidney disease is often called a “silent disease” because it typically has no symptoms in its early stages. For seniors, subtle signs might be mistaken for other age-related issues. Regular check-ups are the best way to catch potential problems before they become severe. A doctor will order a blood test for eGFR and a urine test for albumin, an early sign of kidney damage.
Understanding Your Results: A Comparison
| Assessment | For a 30-Year-Old (Normal) | For a 70-Year-Old (Average) |
|---|---|---|
| eGFR (mL/min/1.73m²) | Typically above 90 | Around 75, but can be lower |
| Significance of eGFR 60-89 | May indicate early kidney disease if accompanied by other signs | Often considered normal, especially without other kidney damage indicators |
| Serum Creatinine (mg/dL) | Men: 0.74-1.35; Women: 0.59-1.04 | Interpreted carefully due to lower muscle mass; a 'normal' reading might mask reduced function |
| Response to Injury | Kidneys have greater reserve and more robust repair mechanisms | Kidneys are more vulnerable to injury from dehydration or medications |
Conclusion
The average kidney function for a 70-year-old is expected to be lower than that of a younger adult due to the normal aging process, reflected by a slightly lower eGFR. It's crucial for seniors to understand that a moderately low eGFR isn't necessarily a sign of a severe problem, especially without other markers of kidney damage like albumin in the urine. Managing underlying health conditions, adopting a healthy lifestyle, and having regular check-ups with blood and urine tests are the most effective strategies for maintaining optimal kidney health and differentiating normal aging from progressive chronic kidney disease. A discussion with a doctor can help determine if lifestyle changes or specific interventions are needed based on individual health profiles.
For more detailed information on kidney health and chronic kidney disease, visit the National Kidney Foundation.
