• Posted October 27, 2025

Dementia Linked To Impaired Toxic Waste Clearance In The Brain

Faulty waste clearance in the brain could be contributing to dementia, a new study says.

Impaired movement of cerebrospinal fluid — the clear liquid that cushions and cleans the brain — predicted people’s risk of dementia later in life, researchers reported Oct. 23 in the journal Alzheimer’s & Dementia.

These waste clearance problems appear linked to heart health risk factors that damage blood vessels in the brain, researchers noted.

The study focused on the glymphatic system, which flushes cerebrospinal fluid through the brain along tiny channels that surround the small blood vessels.

The system flushes toxins and waste materials out of the brain, including the toxic amyloid beta and tau proteins that are considered hallmarks of Alzheimer’s disease, researchers said.

“Our work provides good evidence in a very large cohort that disruption of the glymphatic system plays a role in dementia,” researcher Dr. Yutong Chen, an academic doctor at the University of Cambridge, said in a news release. “This is exciting because it allows to ask: how can we improve this?”

For the study, researchers analyzed MRI scans taken from around 40,000 adults participating in U.K. Biobank, a large-scale health research project in the United Kingdom.

Results showed that three markers associated with impaired glymphatic function could predict a person’s risk of dementia within the next decade:

• The movement of water molecules along the tiny channels of the glymphatic system.

• An enlarged choroid plexus, the brain region that produces cerebrospinal fluid.

• The flow velocity of cerebrospinal fluid into the brain.

Researchers also found that several heart health risk factors — high blood pressure, diabetes, smoking and alcohol — impaired glymphatic function, and as a result increased dementia risk. 

Heart risk factors contribute to blood vessel damage in the brain, which subsequently impacts the glymphatic system operating around those vessels, researchers said.

“We already know the importance of cardiovascular risk factors when it comes to dementia, and our findings further emphasize this link,” senior researcher Hugh Markus, leader of the Stroke Research Group at the University of Cambridge, said in a news release.

“At least a quarter of all dementia risk is accounted for by common risk factors like blood pressure and smoking. If these impair glymphatic function, then we can intervene,” Markus said. “Treating high blood pressure or encouraging people to stop smoking would be an achievable way to helping the glymphatic system work better.”

This means improving glymphatic function might reduce dementia risk, researchers said.

Sleep plays an important role in the glymphatic system, so better sleep might improve waste clearance, researchers said. Medications might also be able to boost the system’s effectiveness.

Addressing heart risk factors also might protect glymphatic function, researchers added. Clinical trials have shown that tight blood pressure control is associated with a 20% reduction in cognitive decline or dementia.

“This study offers us a fascinating glimpse into how problems with the brain's waste clearance system could be quietly increasing the chances of developing dementia later in life,” Dr. Bryan Williams, chief scientific and medical officer at the British Heart Foundation, said in a news release.

“By improving our understanding of the glymphatic system, this study opens exciting new avenues for research to treat and prevent dementia,” added Williams, who was not involved in the study. “It also emphasizes the importance of managing known cardiovascular risk factors, such as high blood pressure, for reducing dementia risk.”

More information

The Cleveland Clinic has more on the glymphatic system.

SOURCES: University of Cambridge, news release, Oct. 23, 2025; Alzheimer’s & Dementia, Oct. 23, 2025