What is CTE, and how many former NFL players have been diagnosed with it?
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(NEXSTAR) – A new study led by researchers out of Massachusetts suggests that among those who have played in the NFL, at least one in four may develop chronic traumatic encephalopathy (CTE), a disease that carries no cure and has only been diagnosed after death.
The study , published in The BMJ, reviewed the hundreds of NFL players who died between 2008 and 2021. Of the more than 1,700 who died, researchers reported that the brains of 338 were studied. Postmortem brain analysis has, so far, been the only proven method of determining whether someone has CTE, a degenerative brain disease.
Of the 338 brains that were studied, it was determined that 315 donors had a CTE diagnosis.
Among players who died within the last six years – a time in which “brain donation was more frequent” – researchers said 235 NFL players donated their brains for analysis. More than 210 were found to have CTE.
Just over 200 of the 338 whose brains were analyzed had been previously diagnosed with dementia. The study found that donors with dementia were later found to have more severe cases of CTE: 94 had Stage 4 CTE, considered the most severe level.
Broadly speaking, CTE impacts how the brain functions. Research has suggested that CTE is “linked to a build-up of abnormal proteins that damage brain tissue and cause brain cells to undergo cell death,” the Centers for Disease Control and Prevention explains .
CTE is often found in people who have experienced repeated impacts to the head, making football players among the most commonly associated with the disease. However, as the Boston University CTE Center notes , the condition has been linked to boxers and soccer and hockey players, as well as those who have served in the military or as first responders. Even athletes who stopped participating in sports in high school and college have been diagnosed with CTE.
Symptoms can take years or decades to develop, experts say. When they do appear, they can last for months or years. The exact symptoms associated with CTE are unclear, but the CDC explains that those who are diagnosed are later described as having “problems with thinking, emotions, mood, suicidal thoughts and/or behaviors that became serious enough to get in the way of normal daily activities.”
“However, having these symptoms does not necessarily mean a person has CTE,” the CDC adds. “It is important to talk to a doctor if you, a family member, or friend have any questions or concerns. Treatments are available to help with many of these symptoms.”
Research to better understand CTE – including how it develops, what risk factors may be associated with it, and how to diagnose it earlier – continues, according to Boston University.
As the latest study found, there have been hundreds of NFL players who, after their brains were studied following their deaths, were diagnosed with CTE. (A 2023 report said that of the 376 former NFL players studied by Boston University’s CTE Center, 345 had been diagnosed with the brain disease.)
Among the most recently diagnosed was former Dallas Cowboys defensive end Marshawn Kneeland , who died by suicide in November following a high-speed chase with police. Boston University researchers analyzed Kneeland’s brain tissue and determined he had Stage 1 CTE.
Aaron Hernandez , whose 2017 death was ruled a suicide, was found to have Stage 3 CTE. He had been in prison at the time of his death in a murder case.
Former Tennessee Titan Frank Wycheck , who died in 2023 after apparently hitting his head in a fall at home, had Stage 3 CTE, his family said. Former NFL Pro Bowl wide receiver Demaryius Thomas had been dealing with depression, anxiety and other CTE symptoms at the time of his 2021 death. His family later confirmed he had Stage 2 CTE.
Irv Cross , a former NFL player turned CBS anchor, was found to have had CTE following his 2021 death. His widow, Liz Cross, told the Associated Press in 2023 that the former Philadelphia Eagles cornerback had experienced depression, mood swings and memory loss that made him not “want to be with people.” Boston University researchers determined Cross had Stage 4 CTE .
Phillip Adams , who spent several seasons in the NFL, fatally shot six people in Rock Hill, South Carolina, before killing himself in 2021. An autopsy later showed he had Stage 2 CTE , Nexstar’s WJZY reported.
Shane Tamura, the man who killed four people in the same New York City building that houses the NFL’s headquarters, was found to have CTE . In a note found on his body, Tamura expressed a grievance with the league – he played football, but never in the NFL – and claimed he suffered from CTE.
The Associated Press contributed to this report.
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