A new study from Boston University's CTE Center has identified more than 60 cases of chronic traumatic encephalopathy, known as CTE, in athletes who were under the age of 30 at the time of their death. This is the largest study looking at neurodegenerative diseases in young people.
Researchers found that about 40 percent of the brains examined had developed some of the earliest signs of the disease, which is associated with repeated head injuries.
The study also includes what the researchers believe is the first case of an American athlete to be diagnosed with the disease.
The report, published Monday in JAMA Neurologydescribes the characteristics of 152 brains donated between February 1, 2008 and September 31, 2022 to the UNITE Brain Bank – the largest tissue repository in the world with a focus on traumatic brain injury and CTE. Of the 152 brains donated, 63 (41 percent) had autopsy-confirmed CTE.
The disease can only be officially diagnosed by an autopsy and has been associated with memory loss, confusion, impulse control problems, aggression, depression, impaired judgment and suicidal behavior.
In contrast to previous studies that primarily examined CTE in professional American football players, the majority of the athletes diagnosed in this study were amateur athletes who played at the youth, high school, and collegiate levels .
“This study clearly shows that the pathology of CTE begins early,” said Dr. Ann McKee, co-author of the study and director of Boston University's CTE Center. “The fact that over 40 percent of young contact and collision athletes in the UNITE brain bank have a CTE is remarkable,” he added, adding that community brain bank studies show that less than 1 percent of the general population has a CTE.
McKee also notes that all of the brains included in the study were donated for a reason.
“[The study] is not a general population study. It's not a prevalence study,” she said. “We get brain donors who are very symptomatic and that's why the family is trying to donate a brain.”
CTE in young donors
CTE is an Alzheimer's-like condition that is most common in former professional football players but has also been found in military veterans, including many who have been exposed to roadside bombs and other types of military blasts.
Previous studies have shown that repeated hits to the head — even without a concussion — can lead to CTE.
Most of the donors analyzed in this current study played soccer (60 percent), followed by soccer (15 percent) and ice hockey (10 percent). Other sports included in the study that led to the diagnosis of CTE are amateur wrestling, rugby and professional wrestling.
The ages of the donors at the time of death ranged from 13 to 29 years. The youngest person diagnosed with CTE in the study was a 17-year-old high school football player, McKee told CNN.
Brain donors who died before the age of 30 were selected to minimize any contribution from age-related diseases, the study authors said.
Because a majority of the previously analyzed CTE samples came from older adults, looking at younger brains may offer an important perspective, said Dr. Julie Stamm, clinical assistant professor at the University of Wisconsin-Madison, who was not involved in the new study.
“As people age, age-related neurodegenerative changes occur and only general degenerative changes occur,” Stamm said. “So looking at the younger brains allows looking at the CTE pathology without all these other comorbid pathologies.”
Another important aspect of the study is that amateur athletes accounted for 71.4 percent of those diagnosed with CTE.
Of the 48 donors diagnosed with CTE who played football, 37 were amateur football players and 11 played for the NFL. The position played did not affect the development of CTE, but those who played longer were more likely to be diagnosed with the disease. On average, those with CTE played football 2.8 years longer than those who did not develop the disease.
“It's fairly universally accepted that CTE is a risk for elite athletes, especially soccer players,” McKee said. “But it shows that CTE can start in very young athletes who are only involved in amateur sport.”
In a study released earlier this year, BU's CTE Center found that nearly 92 percent of the 376 former NFL players studied were diagnosed with CTE.
Because of a lack of data, it's unclear whether CTE is more common in men than women, McKee said.
Only 11 of the 152 brain donors examined in the new study were female, including one positive diagnosis, a 28-year-old college football player who has not been identified.
Earlier this year, scientists in Australia diagnosed the world's first case of CTE in a professional athlete, Australian Football League player Heather Anderson, who was found to have low-stage CTE during an autopsy by scientists at the Australian Sports Brain Bank.
The neurodegenerative brain disease CTE can occur in people who have been subjected to repeated headbutts. The disease is pathologically characterized by accumulation of tau protein in the brain, which can override neuropathic processes.
In this study, McKee says that the most damage observed in athletes diagnosed with CTE was found in the frontal lobe.
“The frontal lobe is very important for judgment and attention. It's also important for things like what we call leadership, planning, and organizing. It might play a role in impulsivity,” she said.
During the analysis, McKee and her team also found structural changes in the brain.
“They were more likely to have what's called a cavum septum lucidum,” McKee said. “It's a membrane that separates the two hemispheres of the brain and is split in the process. And that split membrane was quite common, a lot more common in people with CTE.”
McKee pointed out that people diagnosed with CTE also have evidence of brain atrophy, or shrinking, because their ventricles — cavities inside the brain — are slightly dilated, suggesting they probably lost some brain volume had.
In the new study, all athletes, regardless of whether they had CTE, experienced clinical symptoms, including depression, difficulty controlling behavior and problems making decisions.
Substance abuse was also common, with alcohol abuse in 43 percent of donors and drug abuse in 38 percent.
The study shows that 87 of the 152 donors died by suicide, including 33 donors who also had CTE. But this finding may not be as remarkable as it seems, McKee said.
“The leading cause of death was suicide, whether or not they had CTE, followed by an accidental overdose,” she said, noting that suicide is one of the leading causes of death in younger people.
Data from the US Centers for Disease Control and Prevention shows that suicide was the second leading cause of death for people ages 10 to 14 and 20 to 34 in 2021.
Although CTE can't be diagnosed until after a person's death, McKee says it's important for athletes to treat symptoms, whether or not they're caused by the disease.
“These people need to go to a doctor and be evaluated because most likely these symptoms could be treated, could be reversible and there is no reason to despair,” she said.
While researchers continue to do more research into how repetitive headbutts affect the brain, particularly in younger people, Stamm says there's no evidence that exposure to bumps at a younger age increases the risk of developing CTE.
“If someone had 5,000 lifetime impacts between the ages of 8 and 18 compared to 5,000 between the ages of 14 and 24, their risk would be the same,” Stamm said.
However, if someone starts playing soccer as a young child and continues into adulthood, their risk of developing the disease increases, Stamm said, adding that “total lifetime exposure to repeated brain trauma is the greatest risk factor for CTE.” .”
McKee adds that specifically, the longer someone plays football, the risk of developing CTE doubles every 2.6 years.
Experts say parents of young athletes should tread carefully but not neglect the benefits of the sport.
“I think for parents who are wondering, ‘Should my child play youth or high school football,' we have no evidence that there will be a long-term problem,” says Dr. Steven Broglio, director of the University of Michigan Concussion Center. “It's a bit like smoking: the more you smoke it, the greater the risk.
Although the study found evidence of CTE in some younger people, most with the diagnosis had been exposed to contact sports for much longer.
Broglio adds that it is ultimately an individual decision whether or not a parent wants their child to play contact sports.
“For the average person, the benefits of exercise, whether it's a contact injury or something else, far outweigh the risks,” he said. “But that doesn't mean there's no risk involved in playing a sport.”
CNN's Nadia Kounang contributed to this report.