The study did not demonstrate that poor kidney function directly raises Alzheimer’s biomarker levels. It simply identified a link between the two.

Kidneys play an essential role in clearing waste and toxins from the bloodstream, removing these substances through urine.

How Kidney Health Shapes Biomarker Readings

“Our study found that when the kidneys are not functioning properly, there may be higher levels of Alzheimer’s biomarkers in the blood,” said study author Francesca Gasparini, MD, of Karolinska Institutet in Stockholm, Sweden. “While we did not find that having reduced kidney function increased the risk of developing dementia, we did find that impaired kidney function may accelerate the onset of dementia in people who have higher levels of biomarkers. This highlights the need for doctors to consider kidney function when interpreting results of Alzheimer’s biomarkers in the blood.”

The study followed 2,279 adults with an average age of 72. None of them had dementia at the start. Each participant completed medical exams, cognitive assessments, and blood tests that measured kidney function along with levels of several Alzheimer’s disease biomarkers. These included tau and amyloid beta proteins, neurofilament light chain proteins and glial fibrillary acidic proteins.

Long-Term Tracking of Kidney Function and Dementia

Participants were monitored for about eight years. Among the 1,722 people with healthy kidney function, 221 developed dementia. In the group of 557 individuals with impaired kidney function, 141 developed dementia.

Researchers observed that poorer kidney function correlated with higher levels of most Alzheimer’s biomarkers measured in the study. Removing participants who developed dementia during the follow-up period did not change the overall patterns.

Dementia Risk, Genetic Factors and Biomarker Levels

After adjusting for factors such as age, sex and APOEe4 — a genetic biomarker that indicates a strong risk of Alzheimer’s disease — the researchers found no increased likelihood of dementia for people with impaired kidney function compared to those with healthy kidneys.

However, the study identified a subgroup of individuals with both impaired kidney function and elevated neurofilament light chain levels who had nearly twice the risk of dementia compared to people with preserved kidney function and the same high biomarker levels. Gasparini explained that this may mean kidney health affects the timing of dementia onset in those with elevated biomarkers, even if it does not raise overall dementia risk.

Why Monitoring Kidney Function Matters

“When looking at these biomarkers in older adults, keeping an eye on kidney health may be more important than one might think,” Gasparini said. “Monitoring kidney health may help clinicians better interpret these biomarkers and identify who might be at risk for faster disease progression.”

One limitation of the research is that Alzheimer’s-related biomarkers were measured only once. This means the study could not determine how changes in kidney function over time might influence biomarker levels. In addition, most participants were highly educated and lived in urban areas of Sweden, so the findings may not apply equally to other populations.