• Posted December 1, 2025

Brain's 'Waste Disposal' Impaired in Pro Fighters

High-tech neuroimaging of pro boxers and mixed martial arts (MMA) fighters is revealing potential damage to a system the brain uses to rid itself of waste. 

“When this system doesn’t work properly, damaging proteins can accumulate, which have been linked to Alzheimer’s and other forms of dementia,” explained study lead author Dr. Dhanush Amin, who conducted the study while at the University of Alabama at Birmingham.

Repeat head trauma suffered by pro fighters has long been linked to short- and long-term brain damage. 

New insights into the brain’s glymphatic system — charged with clearing the brain of built-up metabolites and toxins — might help in the early diagnosis of head trauma, he said. 

“If we can spot glymphatic changes in the fighters before they develop symptoms, then we might be able to recommend rest or medical care or help them make career decisions to protect their future brain health,” Amin said in a news release from the Radiological Society of North America (RSNA).

His team will present their findings this week at the RSNA annual meeting in Chicago. 

As the researchers explained, head trauma suffered during sports account for 30% of all brain injuries, and boxing and mixed martial arts account for many such cases.

Over time, repeat head injury has been linked to serious neurodegenerative and neuropsychiatric disorders.

The discovery of the glymphatic system in the brain is a relatively recent one, Amin and his colleagues said.

The system is a network of fluid-filled channels, that is “like the brain’s plumbing and garbage disposal system,” according to Amin. “It’s vital for helping the brain flush out metabolites and toxins.”

The researchers took advantage of data already collected on 280 professional fighters who had been tracked for at least three years as part of the Cleveland Clinic’s Professional Athletes Brain Health Study. 

Of the 280 fighters studied, 95 were already “cognitively impaired” when they entered the study. The research team used a highly specialized form of MRI to look at water movement in and around spaces surrounding the channels of the glymphatic systems of each fighter’s brain.

They tracked changes in glymphatic activity over time (so-called ALPS measurements) especially as it tied to the number of knockouts each fighter had received.

Those measurements were compared to similar scans conducted on 20 healthy subjects, matched to the fighters by age and other demographic factors. 

The higher the score, the better the brain's waste system is working.

“We thought repeated head impacts would cause lower ALPS in cognitively impaired fighters compared to non-impaired fighters,” said Amin, who is now assistant professor of neuroradiology at the University of Arkansas for Medical Sciences.

"We also expected the ALPS measurement to be significantly correlated with the total number of knockouts in the impaired fighters,” he said.

However, there was a surprising finding: At first, impaired fighters tended to have a higher glymphatic index than non-impaired fighters.  

But impaired fighters' index levels began to decline steadily over time as they suffered further injuries to the brain. 

“We believe that the glymphatic index was initially high in the impaired athlete group because the brain initially responds to repeated head injuries by ramping up its cleaning mechanism," Amin said. "But eventually, it becomes overwhelmed. After a certain point, the brain just gives up.”

In contrast, fighters whose cognition was not yet impaired tended to have a lower total glymphatic index.

According to Amin, measurements of an athlete’s glymphatic system activity might be an early diagnostic tool, helping those who care for athletes advise them on how best to prevent brain damage. 

It could also give insights into memory-robbing illnesses beyond head injury, he added. 

“Studying this system gives us a new window into understanding and possibly slowing memory loss,” Amin said. 

Because these findings were presented at a medical meeting, they should be considered preliminary until published in a peer-reviewed journal.

More information

Find out more about head trauma at the U.S. Centers for Disease Control and Prevention.

SOURCE: Radiological Society of North America, news release, Nov. 26, 2025