At least 1 in 4 NFL players who died in a five-year span had CTE, a new study found — but researchers say the number could actually be much higher.
The condition results in cognitive decline including dementia, and disturbing personality shifts including aggression, confusion, depression, lack of impulse control and impaired judgement.
CTE can only be confirmed after death by examining brain tissue, and not every NFL player who died donates their brain to be examined.
Based on the evidence they had, researchers in a study by Mass General Brigham, Boston University and the Concussion & CTE Foundation published a range of what the actual CTE prevalence among deceased NFL players could be — and the estimates are startling.
From 2016 to 2021, a five-year period when researchers received the most brain donations from deceased former NFL players, they found at least 1 in 4 (24.5%) had CTE.
This would be the most conservative estimate, they said — it could be up to 97.7%, though that extreme is also unlikely. Only 1% of people are affected by this condition in the general population.
“We were unfortunately both surprised but saddened to see that the minimum rate was so alarmingly high,” lead author Dr. Daniel Daneshvar told CBC.
“We know what’s causing it,” Daneshvar told the New York Times. “We … have complete control over the risk. And understanding the extent of that risk is one of the steps into making sure that we can mitigate and decrease that risk.”
How CTE shows up
CTE, or chronic traumatic encephalopathy, is caused by repeated blows to the head and is seen in athletes from a number of sports, from ice hockey to boxing, as well as those who have served in the military — though perhaps nowhere has CTE drawn more attention than in the NFL.
Of the 878 former NFL players who died during the five-year span, researchers looked at the brains of 235.
They found CTE in over 90% of the donated brains — and 30% of them had Stage 4 CTE, the most severe form.
In the most severe cases, CTE is associated with dementia, which shows as a decline in memory, language, problem-solving and other thinking skills. This is easier to diagnose, and more likely to appear on medical records in life.
The researchers found that 59.8% of brain donors had dementia, and 18.6% of donors had “neurodegenerative disease” listed as the primary cause of death.
“They had clinical impairment in their thinking and memory that was so severe they couldn’t take care of their own activities of daily living,” Daneshvar told CBC. “Things like grooming themselves or feeding themselves, or managing their day-to-day activities — they couldn’t do it because the pathology was so severe in their brain.”
A number of high-profile NFL players died by suicide, or surrounded by drugs and violence, during the five-year span studied.
In 2021, Phillip Adams, a corner and defensive back, killed six people in South Carolina and himself. In 2017, tight end and convicted murderer Aaron Hernandez died by suicide in prison.
Wide receiver Vincent Jackson died from chronic alcoholism in 2021. His widow said he turned to alcohol and withdrew socially to manage cognitive difficulties.
Autopsies revealed all three had CTE.
The NFL’s long history with CTE
The NFL has been dealing with outcry over lack of protection for players for decades.
In 1994, they formed the Mild Traumatic Brain Injury Committee, which ultimately published a study saying that serious head injuries were impossible in NFL football, and that players recover within an hour.
“NFL players are a highly conditioned, physically fit population accustomed to playing with pain and highly motivated to return to play as soon as possible,” the committee wrote.
They’ve been sued by former players thousands of times for negligence. In 2013, the league agreed to pay $765 million to 20,000 former players.
In a statement about the new study, the NFL said that the league “continuously strives to make the game of football safer, including by implementing strategies to reduce concussions and head impacts.”
Much of the focus has been on preventing the worst head injuries, like concussions. But researchers are pushing for change in this thinking — CTE prevention should focus on reducing any repetitive head impacts.
There is no current direct treatment or cure for CTE, but experts can address symptoms, from physical therapy to behavioral therapy to manage mood swings and depression.
“Help is available,” said senior author Dr. Jesse Mez. “We have treatments for many symptoms believed to be associated with CTE, and in our clinic we find that symptoms can improve with proper medical care.”
