IMPACT

Study: 99% of Examined NFL Players’ Brains Have CTE

Significant evidence that repeated head trauma can cause degenerative disease.

Of the 111 brains of deceased National Football League players studied by neuropathologist Ann McKee, 110 of them had chronic traumatic encephalopathy, a degenerative brain disease believed to be caused by repeated head trauma. A new study published in The Journal of the American Medical Association reports significant scientific evidence that NFL players risk developing CTE, which can arise years after an athlete has stopped receiving repeated blows to the head and can only be diagnosed after death. However, McKee warned “there’s a tremendous selection bias” in her study, given that many families donated brains because the former player had shown CTE symptoms.