Understanding the Kidneys
Your kidneys are two bean-shaped organs, each about the size of a fist, located on either side of your spine below the rib cage. Their main function is to filter waste products and excess fluid from your blood, which is then excreted as urine. They also perform other vital tasks, including regulating blood pressure, balancing electrolytes, producing hormones that create red blood cells, and activating vitamin D for bone health. A typical kidney contains up to a million tiny filtering units called nephrons, which are critical to this process.
How Kidney Function Is Measured
Clinicians assess kidney function using several key indicators, with the Estimated Glomerular Filtration Rate (eGFR) being the most common. The eGFR is a calculation that uses a person's blood creatinine levels, age, sex, and body size to estimate how efficiently the kidneys are filtering blood. Creatinine is a waste product from muscle breakdown, and higher levels in the blood suggest reduced kidney filtration.
Another important test is a urinalysis, which checks for protein, blood, and other substances in the urine. The presence of albumin, a type of protein, in the urine (albuminuria) can be an early sign of kidney damage, even if the eGFR is still in the normal range.
The Normal Decline in Kidney Function with Age
It is a natural part of the aging process for kidney function to decline, even in healthy individuals. This happens for several reasons:
- Loss of Functioning Nephrons: Over time, some of the kidney's filtering units, the nephrons, simply lose their ability to function.
- Reduced Blood Flow: Blood flow to the kidneys naturally decreases with age, impacting their filtering efficiency.
- Changes to Glomerular Membranes: The membranes within the glomeruli (the filtering part of the nephron) can thicken, further hindering the filtration process.
Average Estimated GFR by Age Group
| 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 |
Note: These are average values. Individual results can vary widely based on health, lifestyle, and other factors. An eGFR under 60 for three or more months can indicate chronic kidney disease, but a lower number in a healthy older person does not always signal disease.
Chronic Conditions That Accelerate Kidney Decline
While some decrease in function is normal, several chronic health conditions can speed up this process and lead to Chronic Kidney Disease (CKD).
Diabetes
High blood sugar levels can damage the small blood vessels in the kidneys over time, leading to scarring and impaired filtering ability. This is why people with diabetes require regular kidney function screenings.
Hypertension (High Blood Pressure)
Untreated high blood pressure damages the blood vessels throughout the body, including the delicate blood vessels in the kidneys. This reduces their filtering capacity and can create a vicious cycle where damaged kidneys further contribute to high blood pressure.
Cardiovascular Disease
Heart and kidney health are closely linked. Poor circulation from heart problems, such as congestive heart failure, can affect blood flow to the kidneys, leading to decreased function.
Other Factors
Other risk factors and conditions include obesity, smoking, family history of kidney disease, and the long-term, excessive use of certain medications like NSAIDs (e.g., ibuprofen).
How Seniors Can Protect Kidney Function
Despite the natural aging process, proactive lifestyle choices can significantly support and maintain kidney health well into later years.
Lifestyle Adjustments
- Stay Hydrated: Drinking plenty of water helps the kidneys flush out waste and toxins effectively. Older adults may experience reduced thirst, so it is important to be intentional about fluid intake.
- Exercise Regularly: Moderate, consistent physical activity can help manage weight, blood pressure, and blood sugar, all of which are crucial for kidney health.
- Quit Smoking: Tobacco use damages blood vessels and impairs circulation, slowing blood flow to the kidneys.
- Limit Alcohol: Excessive alcohol consumption can raise blood pressure and put extra strain on the kidneys.
Nutritional Strategies
- Reduce Sodium Intake: High sodium increases blood pressure and fluid retention, straining the kidneys. Limiting processed foods and salty snacks is key.
- Control Protein Intake: For those with existing kidney issues, excessive protein can be burdensome. Consult with a dietitian to find the right balance.
- Watch Potassium and Phosphorus: As kidney function declines, levels of these minerals can build up and cause problems. A dietitian can help create a kidney-friendly meal plan.
Medical Management
- Regular Check-ups: Routine appointments with a primary care provider are essential for monitoring kidney health, especially for those over 60 or with existing risk factors.
- Medication Management: Discuss all medications, including over-the-counter pain relievers and supplements, with your doctor, as some can impact kidney function.
- Screening: Regular kidney function tests (eGFR and urinalysis) are recommended for at-risk individuals to catch problems early, as symptoms often do not appear until later stages.
Conclusion: Taking Control of Your Kidney Health
The decline in kidney function is a normal part of aging, but it is not an inevitable path toward kidney disease. By understanding what is kidney function by age and taking proactive steps, seniors can significantly influence their kidney health trajectory. Managing chronic conditions like diabetes and high blood pressure, adopting healthy lifestyle habits, and staying vigilant with regular medical check-ups are powerful strategies. Early detection through routine screening, especially for those over 60, allows for timely intervention that can help slow or prevent further damage. The journey toward healthy aging includes prioritizing the health of these vital, hard-working organs, ensuring they continue to support a high quality of life.
For more detailed information on living with and preventing kidney disease, consider exploring resources from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) available online at www.niddk.nih.gov.
