The recent news of NFL legend Brett Favre being diagnosed with Parkinson’s disease has sparked renewed discussions about the possible link between this progressive brain disorder and injuries sustained during Favre’s lengthy 20-year football career.

Athletes face the risk of developing brain diseases due to head trauma, and this risk is not confined to chronic traumatic encephalopathy (CTE) alone.

Studies indicate that repeated brain injuries, even those deemed mild, can lead to a higher chance of developing other neurodegenerative conditions, including Parkinson’s disease.

According to the Parkinson’s Foundation, experiencing just one concussion can increase the risk of receiving a diagnosis by 57% later in life.

“Repetitive brain injuries, regardless of their severity, can have serious ramifications in the long run,” remarked Dr. Joohi Jimenez-Shahed, who is the medical director of movement disorder neuromodulation and brain circuit therapies at Mount Sinai in New York City.

A 2018 research study published in Neurology found that individuals who suffered a significant traumatic brain injury have an 83% increased risk of developing Parkinson’s disease.

While the exact relationship between repeated brain trauma, including concussions, and the onset of Parkinson’s remains unclear, experts propose several theories.

Sudden movements or substantial impacts to the head may harm neurons to the extent that their normal functions are disrupted.

“Although the cells themselves might remain intact, their normal functionality could be compromised,” said Jimenez-Shahed.

This dysfunction may lead to the accumulation of harmful proteins, initiating a neurodegenerative cascade.

Experts have pointed out that specific proteins are associated with various diseases. For instance, CTE is linked to the buildup of tau protein, while Parkinson’s disease is notably marked by an accumulation of the alpha-synuclein protein, which represents “a significant pathological feature” of the condition, according to Jimenez-Shahed.

It’s important to note that head injuries alone don’t completely account for Parkinson’s disease. Experts also highlight environmental factors, such as exposure to specific pesticides and chemicals, alongside genetic mutations as potential contributors.

“If various risk factors converge, they can potentially lead to Parkinson’s disease,” explained Christopher Watts, the Dean of the Harris College of Nursing & Health Sciences at Texas Christian University and a researcher in this field. “Not every individual who boxes will develop Parkinson’s other factors must also be involved in conjunction with head trauma.”

The average age for a Parkinson’s diagnosis is around 65, meaning that at 54, Favre falls on the younger side of this range.

Parkinsonism— a term encompassing various brain disorders leading to slow movements, rigidity, and tremors— has been extensively studied in boxers. One iconic boxer, Muhammad Ali, was diagnosed with this condition.

However, research specifically focusing on football players is still developing. A 2023 study in JAMA found that former organized football players had a higher risk of developing either Parkinsonism or Parkinson’s compared to athletes in other sports. But other studies have yielded inconsistent results, according to Watts.

He stated that it’s crucial for researchers to investigate whether a direct link exists.

“Football is integral to American culture,” he concluded. “We need to uncover the truth.”

Favre disclosed his diagnosis during a congressional hearing linked to a significant welfare case in Mississippi, where he is under scrutiny due to his association with Prevacus, a company developing a concussion treatment. While he has not faced criminal charges, he is among over 40 individuals being sued by the state for restitution of funds related to the Temporary Assistance for Needy Families program.