KELLY MCEVERS, HOST:
Researchers at Boston University have been studying the brains of former NFL players and other athletes after death. The brains were donated by the players or their families. And today, a study published in The Journal of the American Medical Association shows some startling findings. Virtually all of the pro football players had the brain disease known as CTE.
Here's NPR's Tom Goldman.
TOM GOLDMAN, BYLINE: The study examined brains of deceased former football players and found 110 of 111 brains of those who played in the NFL had CTE. Chronic traumatic encephalopathy is a degenerative disease linked to head trauma. Symptoms include memory loss, confusion and depression. Researchers studied the donated brains of 202 former players.
Nearly 88 percent of the brains had CTE. The greatest likelihood of disease was in men who played professionally. Dr. Ann McKee is the study's senior author.
ANN MCKEE: You know, we're seeing this in a very large number that participated in football for many years. So while we don't know the exact risk and we don't know the exact number, we know this is a problem in football.
GOLDMAN: This is a continuation of an eight-year study. McKee says the new numbers are startling and indicates CTE is much more common than previously thought. But she acknowledges the study has flaws.
MCKEE: Families don't donate brains of their loved one unless they're concerned about the person. So all the players in this study had - on some level, were symptomatic. So that leaves you with a very skewed representation.
GOLDMAN: Meaning these numbers alone don't indicate an epidemic sweeping the NFL, nor do the study's low numbers for athletes who only played high school football - 3 of 14 had CTE - indicate relative safety for those who played fewer years.
MUNRO CULLUM: You know, we really can't necessarily extrapolate from those particular findings.
GOLDMAN: Dr. Munro Cullum is a longtime sports concussion researcher.
CULLUM: Because we don't actually know what the prevalence of CTE is in any specific population.
GOLDMAN: More comprehensive long-term studies would help. It would also help researchers if they could identify CTE in the living. Right now it can only be identified after death. The new numbers are certain to prompt new questions as to whether tackle football can survive in light of CTE and whether young people should play.
CULLUM: I mean, how far do we go with this in terms of trying to, you know, bubble wrap our kids?
GOLDMAN: But Dr. McKee, who directs the CTE Center at Boston University, says there is cause for concern.
MCKEE: And while I don't - I'm not willing to say that football is doomed and I also am unwilling to make a decision for other individuals, I think there's a risk to playing football.
GOLDMAN: Critics have accused the NFL of ignoring, even covering up problems with concussions and brain disease. In a statement provided to NPR, the league says it appreciates the study's findings and is committed to supporting research into CTE. Tom Goldman, NPR News.
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