CTE Found in 99 Percent of Tested NFL Brains

From the 111 brains of former pro football players tested, 110 showed signs of the degenerative disease

A new study of former NFL players’ brains found that 99 percent of them tested positive for CTE — a degenerative brain disease that is caused by blows to the head and can lead to depression, impulsivity, rage and memory.

In the study, published in the Journal of the American Medical Association, neuropathologist Dr. Ann McKee studied the donated brains of 202 former players and found that of the 111 that played in the NFL, 110 of them had CTE, which stands for chronic traumatic encephalopathy. (Her findings were consistent with her past studies — in September 2015 she concluded that 87 out of 91 NFL players she tested had CTE.)

The brains in the latest study belonged to players between the ages of 23 and 89, and included every position. While many were anonymous, the families of some former NFL stars such as Ken Stabler (who died in 2015 at age 69), Ollie Matson and Ronnie Caveness, made their involvement public.

McKee, chief of neuropathology at the VA Boston Healthcare System and director of the CTE Center at Boston University, has built the largest CTE brain bank in the world. But the brains of some players, including Junior Seau (pictured above), Mike Webster and Andre Waters — were examined elsewhere, the New York Times noted.

Despite the seemingly concrete results connecting head injuries suffered in the NFL with CTE, McKee told the Times there is “tremendous selection bias” in her study because many families donated players’ brains specifically because they showed symptoms of CTE. (Brain scans can identify signs of CTE in living players but can only be identified conclusively by examining the brains of people who have died).

In the study, linemen had the most cases of CTE, due to the number of repeated and seemingly benign, non-violent blows to head that they suffer during their careers. Quarterbacks and linebackers (such as Seau, who committed suicide at age 43 and left a note requesting that his brain be studied for trauma) are also highly at risk. You can read more about the effects of CTE here.

McKee told NPR we “still don’t know what the incidence is in the general population or in the general population of football players.”

The NFL has tried to address the problem of concussions in several ways since the issue entered the public debate, fueled in part by the PBS “Frontline” documentary “League of Denial” and the 2015 Will Smith film “Concussion,” based on a GQ story about Pittsburgh pathologist Bennet Omalu, who helped shed light on the problem.

Last month, the NFL approved the first claims in a $1 billion concussion settlement with former players. It has also changed rules, educated players and invested in new technology to reduce concussions, though critics say the league could always do more.