Your brain health might be linked to how well your kidneys are working, a new study says.

People with impaired kidney function have higher levels of proteins in their blood that are linked to Alzheimer’s disease, researchers reported Dec. 4 in the journal Neurology.

“Our study found that when the kidneys are not functioning properly, there may be higher levels of Alzheimer’s biomarkers in the blood,” lead researcher Dr. Francesca Gasparini, a geriatrician with the Karolinska Institutet in Stockholm, Sweden, said in a news release.

“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.,” Gasparini said. “This highlights the need for doctors to consider kidney function when interpreting results of Alzheimer’s biomarkers in the blood.”

Kidneys help human health by removing waste and toxins from the blood, which are then excreted in urine, researchers said in background notes.

For the study, researchers tracked nearly 2,300 people with an average age of 72, none of whom had dementia at the start of the study.

During a follow-up of eight years on average, 221 people with healthy kidneys and 141 with poor kidney function were diagnosed with dementia.

Results showed that reduced kidney function was associated with higher blood levels of:

• Tau proteins, which form toxic clumps in the brains of Alzheimer’s patients.

• Protein fragments of neurofilament light chain (NfL), which are released from damaged or dying brain cells.

• Glial fibrillary acidic proteins (GFAP), which are produced by cells that heal and protect neurons in the brain and spinal cord.

Poor kidney function was not linked to an increased risk of developing dementia, after researchers accounted for other risk factors, researchers said.

But researchers did find that those with failing kidneys and elevated levels of NfL proteins had nearly twice the risk of dementia as those with healthy kidneys and high NfL levels.

This suggests that kidney health might influence the timing of dementia, Gasparini said, with healthy kidneys protecting the brain by filtering away toxic waste products.

These patients are likely to still develop dementia, but later than those with impaired kidneys.

“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.”