How Kidney Function Changes With Age

Kidneys are essential organs that filter waste, balance fluids, and regulate blood pressure. However, like many bodily functions, kidney performance gradually declines with age. Understanding how kidney function changes over time, why these changes occur, and how to maintain kidney health can help manage and possibly slow down these age-related effects. Here’s a look at the factors impacting kidney function with age, common changes, and steps to support kidney health.

1. Age-Related Changes in Kidney Structure

As we age, the structure of the kidneys undergoes physical changes:

Decreased Kidney Size: Kidneys gradually shrink as we age. The loss of kidney mass is largely due to the reduction in nephrons, the tiny filtering units in the kidneys. Fewer nephrons mean that the kidneys have less capacity to filter waste.

Blood Vessel Stiffening: Blood vessels in the kidneys tend to stiffen with age, reducing blood flow and decreasing filtration efficiency. Stiffened blood vessels are often due to a build-up of plaque, which can lead to high blood pressure and further strain kidney function.

Thickening of Kidney Tissue: Aging kidneys experience tissue thickening, especially in the glomeruli, which are the structures responsible for filtration. This makes it harder for kidneys to process and filter blood.

2. Reduced Glomerular Filtration Rate (GFR)

The glomerular filtration rate (GFR) is a measure of how well kidneys are filtering blood. A normal GFR is around 90 to 120 mL/min for young adults, but this rate declines gradually with age. By age 70, the GFR may reduce to about 60-70 mL/min, even in healthy adults.

A lower GFR means the kidneys take longer to clear waste products from the blood. When GFR falls below a certain level, it can indicate kidney disease. However, a reduced GFR in older adults does not necessarily mean disease—it can simply reflect the natural aging process.

3. Impact of Comorbidities on Kidney Health

Chronic conditions that are more common with age—such as hypertension, diabetes, and cardiovascular disease—directly impact kidney function:

Hypertension: High blood pressure damages kidney blood vessels, decreasing the kidneys' ability to filter blood effectively. Prolonged high blood pressure is a leading cause of kidney disease.

Diabetes: Diabetes can damage nephrons, reducing kidney function over time. Uncontrolled blood sugar can lead to a condition called diabetic nephropathy, a leading cause of kidney failure.

Cardiovascular Disease: Heart health and kidney health are closely connected. A weakened heart can limit blood flow to the kidneys, impairing their function.

These comorbidities accelerate kidney function decline, making it crucial to manage these conditions proactively.

4. Medications and Their Effect on Aging Kidneys

Older adults often rely on medications for various conditions, including blood pressure, pain, and arthritis. Certain medications can place additional strain on the kidneys, especially as kidney function naturally decreases with age:

NSAIDs: Nonsteroidal anti-inflammatory drugs, like ibuprofen and naproxen, can reduce blood flow to the kidneys, causing additional strain.

Diuretics: Often used to control blood pressure, diuretics increase urine output, which can lead to dehydration and strain kidney function.

Antibiotics and Other Prescription Drugs: Some antibiotics and drugs are filtered by the kidneys, meaning the dosage may need to be adjusted to prevent kidney damage in older adults.

It’s essential to review medications regularly with a healthcare provider, especially as age-related kidney changes occur, to avoid unnecessary kidney strain.

5. Fluid Balance and Dehydration Risk

Aging kidneys have a harder time regulating fluid balance, which increases the risk of dehydration. This is partly because kidney function slows and the body becomes less efficient at conserving water. In addition, the sensation of thirst often diminishes with age, leading older adults to drink less water.

Dehydration can worsen kidney function and increase the risk of kidney stones and urinary tract infections (UTIs). Staying hydrated is essential for supporting kidney health, although some people may need to monitor fluid intake based on health conditions like heart disease.

6. Increased Risk of Kidney Disease with Age

The risk of developing chronic kidney disease (CKD) increases with age. According to statistics, nearly half of people over 75 have some level of CKD, though many cases are mild and do not progress to kidney failure.

Age-related kidney disease typically progresses slowly, but certain factors can accelerate it, including untreated hypertension, diabetes, and lifestyle factors. Early detection and regular monitoring can help manage and slow the progression of CKD in older adults.

7. Lifestyle Tips for Maintaining Kidney Health with Age

A few lifestyle adjustments can support kidney health as you age:

Manage Blood Pressure and Blood Sugar: High blood pressure and diabetes are significant risk factors for kidney disease. Regularly monitoring and controlling these factors can help protect the kidneys.

Eat a Kidney-Friendly Diet: Limit sodium, processed foods, and protein-heavy diets, which can burden the kidneys. Foods rich in antioxidants, such as fruits and vegetables, support kidney health.

Stay Hydrated: Aim for adequate water intake to prevent dehydration, but be mindful of individual fluid needs if you have certain health conditions.

Exercise Regularly: Moderate physical activity supports heart health, blood pressure, and kidney function. It also helps manage weight, which reduces the risk of kidney-related complications.

Limit NSAID Use: Use NSAIDs sparingly and only under guidance, as they can impair kidney blood flow.

Avoid Smoking and Limit Alcohol: Smoking and heavy alcohol use contribute to high blood pressure and kidney strain. Quitting smoking and moderating alcohol intake can benefit kidney function.

8. Regular Kidney Function Monitoring

As we age, regular kidney health screenings become increasingly important. Common tests include:

GFR Tests: Measures the filtration rate of kidneys to detect any decline in kidney function.

Urine Tests: Urine tests can detect protein or blood, which are early signs of kidney damage.

Blood Pressure Monitoring: High blood pressure is both a cause and symptom of kidney disease, so regular checks are essential.

Early detection allows for interventions that can slow kidney decline, even if some reduction in kidney function is natural with aging.

While some changes in kidney function are normal with age, certain symptoms may indicate more serious kidney issues. It’s important to seek medical advice if you experience:

Persistent fatigue or weakness

Swelling in the hands, feet, or face

Difficulty concentrating

Changes in urine output, color, or frequency

Shortness of breath or high blood pressure

These symptoms can indicate declining kidney function or other health conditions requiring medical intervention.

Aging naturally affects kidney function, but adopting healthy habits and managing existing conditions can help maintain kidney health. Regular check-ups, a balanced diet, hydration, and mindful medication use play critical roles in supporting kidneys as they age. By understanding and addressing the impacts of aging on the kidneys, individuals can take proactive steps to preserve kidney function and enhance overall health well into their later years.