Hall of Fame quarterback Brett Favre’s announcement that he has Parkinson’s disease is drawing renewed attention to the potential links between collision sports and risk of brain disease.
Favre revealed his diagnosis Tuesday during congressional testimony about his alleged misuse of taxpayer money. The hearing focused on a welfare scandal in Mississippi, but the topic of Favre’s health came up as he discussed losing an investment in a company he said made a “breakthrough concussion drug.”
“I’m sure you can understand why it’s too late for me because I was recently diagnosed with Parkinson’s disease,” Favre said.
Favre played 20 seasons in the NFL, primarily for the Green Bay Packers, and retired 13 years ago. In a 2022 interview with “The Bubba Army” radio show, he estimated he had suffered thousands of concussions.
“Every time my head hit the turf, there was a buzzing or a flashing, but I was still able to play,” he said in that interview. “That’s the scary thing about concussions. It’s the ones that seem minor that do the damage.”
Sports that involve repeated collisions, such as football, boxing and rugby, carry a risk of concussions and other head injuries.
“We know the brain can only take so much, and when you have that kind of trauma — not just sports-related, but any kind of repeated trauma to the brain — we know it’s going to affect it long term,” said Shannon Shaffer, a nurse practitioner at the Cleveland Clinic and a liaison at Rune Labs, a neurology-focused software and data analytics company.
Early research has established a likely link between these activities and Parkinson’s disease, as well as other neurodegenerative diseases such as Alzheimer’s disease, amyotrophic lateral sclerosis (ALS), and chronic traumatic encephalopathy (CTE). Numerous studies have shown that a single concussion can increase the risk of being diagnosed with Parkinson’s disease by more than 55%.
The NFL did not immediately respond to a request for comment on Favre’s diagnosis and the link between football and neurodegenerative diseases.
Last year, a study found that having played football was associated with a 61% higher likelihood of experiencing symptoms of Parkinson’s disease or being diagnosed with the disease. A 2018 study also found that repeated head impacts from years of playing contact sports were associated with precursors to Parkinson’s disease.
Hannah Bruce, author of the 2023 study, said it can be difficult to determine what role, if any, football played in a case like Favre’s.
“It’s hard to say whether it’s specifically because of football or whether it just increased his risk or his chances of developing Parkinson’s, or whether there are other factors at play,” said Bruce, who led the study at Boston University’s Alzheimer’s Disease Research Center. “But we’re seeing more and more football players coming forward. That says a lot.”
Neurologists who treated boxing legend Muhammad Ali concluded in 2022 that his medical history supported a diagnosis of early-onset Parkinson’s disease, but they were unable to link the disease to head trauma. Ali died in 2016.
Parkinson’s disease is a neurodegenerative disease that causes nerve cells in the brain to weaken and die. It can cause tremors, muscle stiffness, balance problems, and difficulty walking and talking. To reduce symptoms, patients often take prescription medications or receive deep brain stimulation, which sends electrical impulses to nerve cells in the brain.
Repeated trauma to the brain is known to be a potential trigger for the disease, as it can cause inflammation that leads to the death of more nerve cells over time. But it’s one of many risk factors, including older age, underlying genetic susceptibility and exposure to certain pesticides.
Dr. Kevin Crutchfield, a neurologist at Hackensack Meridian Health, said doctors usually rule out other factors before making a link between Parkinson’s disease and football-related injuries.
“The default behavior is not, ‘Oh, you played football, you have Parkinson’s,'” he said.
Crutchfield added that tens of thousands of men have played in the NFL and to date there has not been a surge in Parkinson’s diagnoses among them. But the disease is not always easy to diagnose and symptoms do not necessarily appear quickly after a head injury.
Thor Stein, director of molecular research at Boston University’s CTE Center and a co-author of the 2023 study, said that in some cases, CTE can be a trigger for Parkinson’s disease. Many former football players show signs of the brain disease, which can only be diagnosed after they die.
“The more you get hit repeatedly in the head, the longer you’re exposed to it, the more likely you are to develop a number of different degenerative diseases, including CTE and Parkinson’s disease,” Stein said. “And more recently, surprisingly, we’ve found that in people who develop these symptoms, it’s often not the typical pathology, but often it’s CTE that’s causing the Parkinson’s symptoms.”
In a July study of brain donors diagnosed with CTE, Stein and his co-authors found that nearly a quarter of them had signs of Parkinson’s disease.
Favre said in a 2021 interview with TODAY that he wasn’t sure if he had an ETC.
Crutchfield said it’s important for players to take breaks after a head injury to avoid more serious brain damage.
“The brain is much more susceptible to repeated blows if your brain hasn’t had enough time to heal,” he said. “So athletes hiding a concussion because they want to keep playing is not a good thing.”
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