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Jay Cutler #6 of the Chicago Bears is tackled by Bobby Wagner #54 and K.J. Wright #50 of the Seattle Seahawks at Soldier Field on December 2, 2012 in Chicago, Illinois. The Seahawks defeated the Bears 23-17 in overtime.
Scientists at Boston University's School of Medicine have examined the brains of deceased athletes and military veterans who had suffered from repeated head injuries
The study found that 80 percent showed evidence of chronic traumatic encephalopathy, also known as C.T.E.
We're joined by ESPN reporter Steve Fainaru, who is working on a book about football and brain injuries as well as an upcoming Frontline documentary on the same subject.