Brett Favre, head injuries, Parkinson's: Neurologist says disease cause a 'mystery' (2024)

NFL Hall of Fame quarterback Brett Favre's recent announcement that he had been diagnosed with Parkinson's disease raised questions about whether head injuries he suffered during his time on the gridiron could have sparked the degenerative neuromuscular condition.

Researchers, in fact, have been exploring whether there's a link between concussions and Parkinson's since about 2012, saidDr. Melinda Burnett, aneurologist with the CHI Health Neurological Institute in Omaha.

While head injuries, pesticides and family history are considered risk factors, they're not strong ones, she said, particularly compared to the potent link between smoking and lung cancer.

"The thing to remember about Parkinson's disease is that we still have not found the cause," said Burnett, who specializes in Parkinson's and other movement disorders and has a special interest in the connection between traumatic brain injuries and neurodegenerative conditions.

Thomas Burnett also played briefly for the San Diego Chargers before retiring from football, earning a doctorate and spending more than 40 years as a teacher, administrator and handball coach at Missouri State University.

He donated his brain to a Boston University tissue bank that collects samples from deceased athletes to better understand the effects of trauma on the human nervous system. Dr. Ann McKee and her team there have published a number of studies focused on chronic traumatic encephalopathy, or CTE. Researchers there define the condition as a progressive, degenerative brain disease found in people with a history of repetitive brain trauma.

Melinda Burnett said researchers identified proteins linked to both Parkinson's and CTE in her father-in-law's brain. Not only are the two conditions characterized by different proteins, they also cause different symptoms while sufferers are alive.

Symptoms of Parkinson's include tremors, slow movement and muscle stiffness. CTE symptoms, according to the Boston center, include memory loss, confusion, impaired judgment, aggression and depression and often begin years or even decades after the last brain trauma or end of active athletic involvement.

Because it's tied to suchdramatic changes and has been widely reported, Burnett said, CTE has somewhat overshadowed Parkinson's.

Favre was diagnosed with Parkinson's in January after he began having trouble using his right arm, the Associated Press reported. He once estimated he had "thousands" of concussions during his playing career, which included nearly 20 years in the NFL.

Burnett walked through some of what researchers currently know— and don't know— about Parkinson's and head injuries.

Parkinson's itself, she said, is relatively common. Between 1% and 2% of people will experience it over their lifetime. Rates increase as people get older, with between 3% and 4% of those in their 80s having the condition.

"In fact, we're in the middle of an epidemic of sorts," Burnett said. "Since our population is aging, Parkinson's is getting more prevalent."

Researchers have identified risk factors, such as pesticide exposure and family history. But neither are strong. Plenty of people who have gotten Parkinson's have had little exposure to pesticides, she said. And most have no family history of the disease.

"It's still a big mystery why people get the disease," she said.

Scientists also have spent the past decade trying to determine how strong a risk factor is posed by concussions and traumatic brain injuries.

One challenge is that people often don't realize— or remember— thatthey've had a concussion. In past decades, players often didn't acknowledge that they'd suffered such injuries. It wasn't part of the culture.

"This is our problem," Burnett said. "That generation who is now older, would not even know how to count their concussions."

Her father-in-law, who also played football for the University of Arkansas, never revealed how many impacts he suffered, she said. He also had been in a car wreck and may have suffered a head injury in the accident.

What does the research say about Parkinson's and head injuries?

As with family history and pesticides, researchers have found an association between concussions and Parkinson's. However, they have not yet shown it to pose a greater risk than those other factors.

A study of veterans in 2018 found that those who had at least one concussion had a 57% higher risk of getting Parkinson's, she said. But while the number sounds large, it would only increase the number of people who get the condition by about a half a percent.

Researchers are starting to see a somewhat stronger association with more serious injuries. One study, but not all, indicated that a concussion that rendered people unconscious for an hour or more tripled the risk of Parkinson's, which is a factor of three, Burnett said. However, the absolute risk remains low. Smoking, by comparison, raises the risk of lung cancer by a factor of 100.

In another study, on the other hand, Mayo Clinic researchers studied people who had played high school football in the 1950s without helmets or protective gear and found no increased risk of Parkinson's.

Other research, however, has pointed to a kind of "dose response" based on how long people played football, she said, with high school players having a lower risk than collegiate athletes and college players having less exposure than professional football players.

A 2023 paper published in the Journal of the American Medical Association Network Open found the risk of developing Parkinson's increased for all football players, regardless of the level or duration of play, but playing professionally increased the risk by a factor of three.

Studying the dose response is important, Burnett said, because establishing a connection between two factors, such as concussions and Parkinson's, is interesting but it's not enough to prove one causes the other. Showing that increasing one factor, such as severity or frequency of head injuries, increases the other strengthens the argument for causality.

"More studies are needed to really pick out the mechanism there and how much we should worry about it," she said.

The good news, she said, is that parents, players and sports officials at all levels of play now are taking head impacts and injuries more seriously.

At the same time, scientists and others are trying to identify additional ways to mitigate risk, such as breaks in play. Cognitive testing, which isn't used to diagnose concussions but to manage it, means players are more likely to be sidelined until they're determined ready to return. In particular, there is less risk of a dangerous double hit, or back-to-back concussions.

"We're more cautious now, and so it's a different ballgame," Burnett said.

Meanwhile, scientists also are looking for biomarkers, such as a blood test or brain scan, that might clear an athlete for play or signal that they need more time to recover.

Burnett is part of a team at Creighton University School of Medicine conducting an early-stage clinical study to look for tiny particles, released by brain cells, in patients' blood with the ultimate goal of developing a blood test that could be used to diagnose Parkinson's.

Currently, there's no specific test for the condition. Making the call comes down to reviewing patients' medical histories, looking at their symptoms and conducting a neurological and physical examination. Ultimately, doctors give patients a medication used to treat Parkinson's. If they respond —and have the right symptoms —a doctor can diagnose the disease.