Boston University School of Medicine researchers studied the brains of 202 former athletes who had played football in the NFL, the Canadian Football League or at the college or high school level and found signs of CTE in the brains of 110 of the former 111 NFL players.
The condition, which currently can be diagnosed only by taking brain tissue from a dead subject, has been diagnosed in former players including Hall of Fame linebacker Junior Seau and Pro Bowl safety Dave Duerson, who both committed suicide.
"I can also say, with certainty, some players now are genuinely scared. I'm hearing a level of concern I haven't heard before," Freeman wrote in an article for Bleacher Report.
"I've heard from some who say the latest story and data regarding CTE rocked them more than any other. It was the near 100 percent number that triggered it. Some players tell me now they don't see it any other way: If you play in the NFL, you will get CTE. It's that simple to some of them."
The NFL, which last year pledged $100 million for neuromedical research, said the study would help the league and players to understand the condition. "The NFL is committed to supporting scientific research into CTE and advancing progress in the prevention and treatment of head injuries," said NFL spokesman Brian McCarthy, in an email.
The study found signs of CTE in the brains of 91 per cent of the 53 former college players whose brains were studied and 21 per cent of the former high school players.
