Dr. Ann McKee, a neuropathologist, has examined the brains of 202 deceased football players. A broad survey of her findings was published on Tuesday in The Journal of the American Medical Association.
Of the 202 players, 111 of them played in the N.F.L. — and 110 of those were found to have chronic traumatic encephalopathy, or C.T.E., the degenerative disease believed to be caused by repeated blows to the head.
C.T.E. causes myriad symptoms, including memory loss, confusion, depression and dementia. The problems can arise years after the blows to the head have stopped.