In the movie Concussion, Will Smith plays the doctor who discovered the condition known as chronic traumatic encephalopathy, or CTE, in pro football. The film’s release this month follows years of headlines on the risks NFL players face as they suffer crushing blows and tackles every week.
Researchers analyzed 66 brains donated for study from men who played high school or college contact sports and found that one-third of them had CTE. In a comparison group of 198 donor brains from people with no record of playing contact sports, none had CTE.
While a relatively small sample and not necessarily representative of the general population, that’s a striking difference. “The findings have important implications for public health given the number of individuals with past exposure to contact sports,” the authors wrote in the report, published on Dec. 1 in the journal Acta Neuropathologica.
CTE is characterized by degeneration of brain tissue that can cause memory loss, behavioral problems, and depression. It can only be confirmed after death, which makes measuring the disease in the population tricky.
Concerns over safety in amateur sports are increasing as the extent of brain damage in professional athletes becomes more evident. Youth soccer organizations in the U.S. recently limited the practice of heading the ball for younger children. That change was part of the resolution of a class-action lawsuit against soccer organizations seeking rule changes to improve safety.
The new study was an attempt to gauge how common CTE might be among amateur athletes, rather than “selectively recruited athletes” like NFL players, said Kevin Bienek, a neuroscience researcher at the Mayo Graduate School and lead author on the paper with colleagues from Mayo and Boston University.
“Researchers have known that they’ve received a lot of concussive hits,” he said. “Our approach was more, ‘What is the frequency of CTE in the general population?’”
The small size of the study, however, should give pause to anyone tempted to say that high school football players definitely run the same risks as, say, a Dallas Cowboys offensive lineman.
“This is a very select sample,” cautioned Gerard Gioia, division chief of neuropsychology at Children’s National Health System in Rockville, Md. “One shouldn’t overinterpret the findings to suggest that contact sports is going to produce CTE in one-third of us.”
The research team used sources including clinical records and obituaries to determine which brains in the Mayo Clinic’s Jacksonville (Fla.) brain bank belonged to former amateur athletes. Those selected had played football or baseball, boxed, or wrestled, among other sports, with some having participated in more than one. The average age of death was 78, so the playing days of the subjects occurred decades ago—a factor that may mean they had less effective protective gear than what’s available today.
Among members of the nonathlete control group, some also had brain injuries—from a fall, a car crash, or an assault, for example. Those cases didn’t seem to trigger CTE, the study found.
What the study doesn’t show—and further research needs to examine—is how many people whose brains show signs of CTE after death have manifested symptoms during life, said Robert Cantu, a clinical professor of neurosurgery at Boston University School of Medicine.
“We don’t know whether these brains were symptomatic or not when these people lived,” Cantu said. “And that would be hugely important to know.”
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