Kidney Function and Alzheimer’s Biomarkers
Kidney function may influence the levels of Alzheimer’s-related biomarkers found in the blood, according to research published on December 3, 2025, in Neurology, the medical journal of the American Academy of Neurology. The study found that older adults with impaired kidney function tended to have higher blood levels of several biomarkers associated with Alzheimer’s disease and neurological damage.
However, the researchers did not find that reduced kidney function increased a person’s overall likelihood of developing dementia. The findings instead suggest that kidney health may affect how certain blood test results should be interpreted, especially in older adults being evaluated for memory loss or cognitive decline.
It is important to understand that the study identified an association rather than a direct cause-and-effect relationship. Reduced kidney function was linked to higher biomarker levels, but the research did not prove that kidney disease directly caused those levels to rise.
Kidney Function May Affect Biomarker Readings
The kidneys continuously filter the blood, remove metabolic waste and help eliminate unwanted substances through urine. When kidney filtration declines, certain proteins and waste products may remain in the bloodstream longer than they normally would.
Researchers have questioned whether reduced clearance could influence the concentration of Alzheimer’s-related proteins detected in blood tests. This study provides additional evidence that kidney health should be considered when doctors evaluate neurological biomarkers.
Study author Francesca Gasparini, MD, of Karolinska Institutet in Stockholm, Sweden, explained that people whose kidneys were not functioning properly showed higher blood levels of Alzheimer’s biomarkers.
Although impaired kidney function was not associated with a higher overall incidence of dementia, it appeared to affect the timing of dementia among some people who already had elevated neurological biomarkers.
This distinction is important. A high blood biomarker result does not automatically mean that a person has Alzheimer’s disease or will develop dementia. Kidney filtration, age, cardiovascular health, medications and other medical factors may influence the result.
Understanding Alzheimer’s Blood Tests
Alzheimer’s biomarkers are measurable biological substances that can provide information about changes occurring in the brain and nervous system. Blood-based biomarker testing is becoming increasingly important because it is generally less invasive than a spinal tap and more accessible than specialized brain imaging.
The researchers examined several biomarkers associated with Alzheimer’s disease, inflammation and nerve-cell damage.
Tau Proteins and Kidney Health
Tau proteins normally help support the structure of nerve cells. In Alzheimer’s disease, abnormal forms of tau can accumulate and form tangles inside the brain.
Certain forms of tau can also be measured in the bloodstream. Higher blood levels may indicate neurological changes, but reduced kidney clearance may influence how long these proteins remain in circulation.
This means elevated tau levels should not be interpreted without considering a patient’s kidney health, cognitive symptoms and overall medical condition.
Amyloid Beta
Amyloid beta is a protein involved in the formation of plaques commonly associated with Alzheimer’s disease. Blood tests may measure different forms or ratios of amyloid beta to estimate the likelihood of amyloid-related changes in the brain.
The study found that poorer kidney health was associated with differences in several Alzheimer’s-related measurements, including amyloid biomarkers.
However, an abnormal amyloid beta result does not confirm dementia by itself. Doctors may need to combine blood testing with cognitive assessments, medical history, neurological examinations and other diagnostic tools.
Neurofilament Light Chain
Neurofilament light chain, commonly abbreviated as NfL, is released into the bloodstream when nerve cells are damaged.
Elevated NfL is not specific to Alzheimer’s disease. It may also occur with other neurological disorders, brain injuries and age-related changes.
The study identified an especially notable relationship involving impaired kidney filtration and elevated NfL. People with both conditions appeared to face a greater likelihood of developing dementia earlier than people with preserved kidney filtration and similarly high NfL levels.
GFAP and Renal Health
Glial fibrillary acidic protein, or GFAP, is associated with specialized brain cells called astrocytes. Higher blood levels may reflect inflammation, injury or other changes within the nervous system.
Poorer renal health was associated with higher levels of most of the biomarkers measured in the study, including markers connected with neurological stress.
These findings reinforce the need to evaluate kidney filtration when reviewing blood tests related to cognitive and brain health.
How the Study Was Conducted
The research included 2,279 adults with an average age of 72. None of the participants had dementia at the beginning of the study.
Each participant underwent medical examinations, cognitive testing and blood testing. Researchers measured kidney function and evaluated levels of Alzheimer’s-related and neurological biomarkers.
Participants were then monitored for approximately eight years to determine who developed dementia.
Among the 1,722 people with healthy kidney function, 221 developed dementia during the follow-up period. Among the 557 participants with impaired kidney function, 141 developed dementia.
At first glance, these numbers might appear to suggest a direct relationship between reduced kidney health and dementia. However, participants with impaired kidney function may have differed from the healthy-kidney group in other important ways, including age, medical history and genetic risk.
Researchers therefore adjusted their analysis for several factors that could influence a person’s likelihood of developing dementia.
Reduced Kidney Function Did Not Raise Overall Dementia Risk
After accounting for age, sex and APOE ε4 status, researchers did not find that impaired kidney health independently increased the overall likelihood of dementia.
APOE ε4 is a genetic variant associated with a substantially higher risk of developing Alzheimer’s disease. Adjusting for this factor helped researchers separate the possible effects of kidney health from an established genetic risk factor.
The lack of an increased overall dementia risk is one of the study’s most important findings. The results should not be interpreted to mean that people with chronic kidney disease will necessarily develop Alzheimer’s disease.
Instead, reduced filtration may influence blood biomarker concentrations and possibly the timing of dementia onset in people who already show signs of neurological injury.
Researchers also removed participants who developed dementia during the follow-up period and repeated portions of the analysis. The general relationship between impaired filtration and higher biomarker levels remained.
A Higher-Risk Subgroup
Researchers identified a notable pattern among participants who had both impaired kidney function and elevated neurofilament light chain levels.
People with this combination had nearly twice the dementia risk of participants who had preserved kidney function but similarly high NfL levels.
This does not prove that kidney impairment caused dementia. Instead, it suggests that reduced filtration may be particularly important among people who already have evidence of nerve-cell damage.
Gasparini explained that kidney health may influence when dementia begins in people with elevated biomarkers, even though it does not appear to increase dementia risk across the entire population.
Additional research is necessary to understand why this combination was associated with faster or earlier progression.
Why Doctors Need More Context
Blood-based Alzheimer’s testing may eventually become part of routine evaluations for people experiencing memory loss, confusion or other cognitive symptoms.
As these tests become more widely used, clinicians must understand which health conditions can affect their accuracy and interpretation.
A higher biomarker level could reflect neurological changes, reduced removal from the bloodstream or a combination of both factors. Doctors may therefore need to evaluate estimated glomerular filtration rate, creatinine and other measures of renal health alongside Alzheimer’s blood tests.
A biomarker result should not be interpreted in isolation. Medical history, cognitive testing, neurological examinations, medications, kidney health and other laboratory findings may all provide essential context.
The findings do not mean Alzheimer’s blood tests are unusable in people with kidney disease. They indicate that the results may require more careful interpretation.
Monitoring Kidney Health in Older Adults
Kidney filtration commonly declines with age, even among people who have never been diagnosed with chronic kidney disease.
Diabetes, high blood pressure, cardiovascular disease, dehydration and certain medications may also affect renal health.
Older adults undergoing cognitive evaluations may benefit from routine kidney monitoring, particularly when Alzheimer’s biomarker tests are being considered.
Monitoring kidney function can help doctors determine whether reduced filtration may be contributing to elevated biomarker readings.
Tests Doctors May Consider
Common kidney health measurements include:
- Serum creatinine
- Estimated glomerular filtration rate
- Urine albumin-to-creatinine ratio
- Blood pressure
- Blood glucose or A1C
- Medication and supplement review
Regular testing may help clinicians identify kidney changes early and determine whether impaired filtration could be influencing Alzheimer’s-related blood test results.
People should not attempt to diagnose Alzheimer’s disease or kidney disease from a single laboratory value. Test results must be reviewed by qualified healthcare professionals who understand the person’s complete medical history.
Important Study Limitations
The study had several limitations. Alzheimer’s-related biomarkers were measured only once, so researchers could not determine how changes in kidney function affected biomarker concentrations over time.
Repeated testing would be needed to establish whether worsening or improving filtration produces corresponding changes in blood biomarker levels.
Most participants were highly educated adults living in urban areas of Sweden. The findings may not apply equally to people with different educational, racial, geographic or socioeconomic backgrounds.
The study was also observational. It identified relationships between kidney health, biomarker levels and dementia outcomes but could not establish that one factor directly caused another.
What the Findings Mean
This research adds an important layer to the interpretation of Alzheimer’s blood biomarkers. Reduced kidney function was associated with higher levels of several biomarkers, but it was not independently linked to a higher overall risk of dementia.
The findings suggest that elevated biomarker levels may not always have the same meaning in every patient. Kidney filtration may influence how much of a biomarker remains in the bloodstream and may help identify people at risk for faster progression when neurological injury is already present.
As blood tests for Alzheimer’s disease become more common, evaluating renal health alongside neurological biomarkers may improve diagnostic accuracy and prevent results from being interpreted without proper medical context.
Maintaining kidney health remains important for overall well-being, cardiovascular health and the body’s ability to clear metabolic waste. However, this study does not show that improving kidney health will lower Alzheimer’s biomarkers or prevent dementia.
Anyone concerned about memory changes, abnormal biomarker results or declining kidney filtration should discuss the findings with a physician rather than drawing conclusions from a single blood test.
