Almost 90 percent of brains examined from deceased professional football players showed signs of disease, according to a study published Tuesday in the Journal of the American Medical Association.
The study was conducted by researchers at Boston University School of Medicine and the VA Boston Healthcare System.
Chronic traumatic encephalopathy, or CTE, was diagnosed in 177 out of 202 subjects who had played football for at least 15 years. The diagnosis was made in the cases of three high school players, 48 college players, nine semi-professional football players, seven Canadian Football League players and 110 NFL players. Only one NFL athlete who had donated his brain to the study was not found to have CTE, a debilitating disease that can cause a range of symptoms including memory loss.
CTE was diagnosed in 110 of 111 brains from former NFL players.
The NFL, responding in a statement, underlined that even the study’s authors have called for further research and pointed out that the league had donated $200 million to medical and neuroscience research to better understand the long-term effects of head trauma and CTE.
“As noted by the authors, there are still many unanswered questions relating to the cause, incidence and prevalence of long-term effects of head trauma such as CTE. The NFL is committed to supporting scientific research into CTE and advancing progress in the prevention and treatment of head injuries.”
The study doesn’t confirm the presence of CTE in all football players. Its authors point out that athletes who have dealt with CTE symptoms were likely more motivated to donate their brains to research.
Still, the results are startling for the millions of players and families involved with the nation’s most popular sport, from Pop Warner through high school, college and the NFL.
Among the brains studied, 84 had severe CTE. The authors said 89 percent of those subjects suffered from behavioral or mood symptoms or both, 95 percent had cognitive problems and 85 percent had signs of dementia, according to the authors.
“There are many questions that remain unanswered,” said lead author Dr. Ann McKee, a Boston University neuroscientist. “How common is this in the general population and all football players? How many years of football is too many?”
It’s also unclear, she said, whether lifestyle habits — alcohol, drugs, steroids, diet — impacted the results.
People who suffer from CTE can exhibit a number of symptoms, including mood and behavioral changes soon after head trauma and severe neurological disorders later, according to the Concussion Legacy Foundation, which is associated with the study institutions.
Research into CTE is relatively new. A direct link between head trauma and CTE was firmly established in 2005 by pathologist Bennet Omalu, who confirmed the syndrome in former Pittsburgh Steeler Mike Webster. The former NFL player suffered from “physical and psychological turmoil” before his death from a heart attack at age 50, as described in an obituary in The New York Times.
The story was dramatized in the 2015 film “Concussion,” starring Will Smith as Dr. Omalu.
Although it sometimes feels as though concussion risks pose an existential threat to the game, the NFL is the most popular professional sports league in America and more high school students play 11-man football than any other sport.
Last year, the National Federation of State High School Associations reported that 1,083,308 high school boys and nearly 2,000 girls played football, more than the combined total participating in outdoor track and field (1,077,102) soccer (821,851) or basketball (975,808), which have high participation rates across genders.
There has been some decline. In 2015, The MMQB reported that participation rates for high school football had gone down in six of the previous seven years and had fallen 2.5 percent overall since 2008-2009. Former players and coaches including Mike Ditka, Terry Bradshaw and Brett Favre have said they wouldn’t let their young sons play the game or would have serious hesitations.
The latest research could give them and others even more pause.
The NFL first acknowledged the link between playing football and CTE in 2016, when Jeff Miller, the NFL’s senior vice president for health and safety, answered a question from Rep. Janice D. Schakowsky, Illinois Democrat, at a roundtable discussion on concussions set up by the House Committee on Energy and Commerce.
Ms. Schakowsky asked Mr. Miller if scientific research had established a link between football and neurodegenerative diseases.
“The answer to that question is certainly yes,” Mr. Miller said, according to ESPN. Mr. Miller went on to reference Dr. McKee’s research in his answer.
That was the first time a senior league official had clearly acknowledged a connection. The NFL followed up Mr. Miller’s comment with a statement saying that his words “accurately reflect the view of the NFL.”
Still, the issue is far from settled among major figures in the league. At last year’s owners meetings, Dallas Cowboys owner Jerry Jones told reporters that it would be absurd to say there was a relationship between playing football and having the neurological disease.
The NFL was not required to admit any fault as part of a $1 billion concussion settlement intended to put an end to thousands of lawsuits filed by former players in 2013. The settlement was appealed after Mr. Miller’s comments, but a federal appeals court upheld the ruling in April 2016.
Dr. McKee and her fellow researchers said more study is needed.
“This is the largest and most methodologically rigorous case series of individuals diagnosed with CTE ever published — all the participants were exposed to a relatively similar type of head trauma while playing football,” Dr. Michael Alosco, a co-author of the McKee study, wrote in an email to The Washington Times. “It provides a rich source of data on the clinical and pathological features of CTE, which has never been previously reported on.”
But more needs to be done, Dr. Alosco said.
“While we found CTE in former high school players, we need to do further research to better understand the risks associated with playing football in high school (and earlier) and determine how exactly repetitive head impacts lead to CTE,” he wrote.
• This article is based in part on wire reports.