111 NFL players' brains were examined. All but 1 had CTE.

Of the 111 brains of deceased NFL players examined in a study published Tuesday in The Journal of the American Medical Association, all but one of the brains showed signs of the neurodegenerative brain disease chronic traumatic encephalopathy (CTE). The disease, found in 110 of 111 NFL players' brains donated for scientific research, is "linked to repeated blows to the head," The New York Times reported. Symptoms of CTE, which can only be diagnosed with an autopsy, include memory loss, confusion, and depression.

The players whose brains were examined spanned every position, from quarterbacks to running backs to linemen. Some players, such as Hall of Famer Ken Stabler, were particularly famous, while others were lesser known. In addition, high school and college players' brains were examined; CTE was found in three of 14 high school players' brains and 48 of 53 college players'.

Neuropathologist Ann McKee warned that there's "a tremendous selection bias" in the study's sampling of brains because the families that donated the brains oftentimes did so because they suspected symptoms of CTE. However, McKee noted the "fact that we were able to gather this many cases" in just the past eight years suggests the disease is "much more common than we previously realized."

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McKee acknowledged that it's still not clear "what the incidence is in the general population or in the general population of football players," but she said one thing is clear: "It is no longer debatable whether or not there is a problem in football — there is a problem."