Study finds signs of CTE in 99% of NFL players’ brains

Evidence of chronic traumatic encephalopathy (CTE), a progressive degenerative disease found in people who have received repeated blows to the head, was discovered in the brains of 110 out of 111 (99%) former National Football League players, a newly published study has revealed.

The research, published Tuesday in the Journal of the American Medical Association, also found signs of CTE in 48/53 former college football players; 7/8 Canadian Football League players and 3/14 high-school players. Neither of the two pre-high school showed evidence of the disease.

The three high school players had mild cases of CTE, while the rest of the ex-players had a mix of mild-to-severe symptoms, according to Ars Technica – who pointed out that the brains were a “convenience sample” or a biased sampling that is not representative of ex-athletes as a whole.

A total of 202 former brains were donated for analysis by the former players or their families due to concerns or suspicions that they were at risk for developing CTE. While the study provides no new information about the disease and its progression, it does strengthen the apparent association between football and CTE, a condition that can cause aggression, depression and dementia.

“It’s impossible to ignore this anymore,” study author Dr. Ann McKee, a neuropathologist from Boston University, told the Boston Globe. She said that her team was “startled” by the extreme prevalence of CTE among the brains that were analyzed, adding that the results confirm that this is “a public health problem… something that should concern parents and athletes.”

Data strengthens link between CTE and football, say authors

First discovered in boxers in the 1920s and originally known as dementia pugilistica, CTE can only be diagnosed by post-mortem examination of the brain, according to Ars Technica. Doctors search for unusual protein masses accumulate near tiny blood vessels. Those lumps are limited to the outer layers of the brain in mild cases but are found in deeper areas in severe instances.

As part of their research, Dr. McKee and her colleagues examined the brains of 202 individuals who had played football at various levels at some point during their lives. Of those ex-players, a total of 177 (87% of them) showed pathological evidence of CTE – a high proportion which the study authors said suggests that the disease may be linked to prior participation in the sport.

Eighty-four of the participants were found to have severe signs of CTE in their brains, while 27 had mild pathology, the researchers reported. Of those with severe CTE, 80 were found to have cognitive symptoms related to the disease, while 75 had behavioral and/or mood symptoms and 71 showed evidence of dementia. Among those with mild CTE, 26 had behavioral and/or mood symptoms, 23 had cognitive symptoms and 9 showed signs of dementia.

“The fact that we were able to gather so many instances of a disease that was previously considered quite rare… speaks volumes,” Dr. McKee said in a statement. “Our goal is to try to understand the disease from its earliest beginnings in the brain, what molecular pathways are involved, how it spreads, which regions it affects most severely – all to give us ideas how to diagnose this disease during life, and also to give us information about how to treat it.”

“We appreciate the work done by Dr. McKee and her colleagues for the value it adds to the ongoing quest for a better understanding of CTE,” the NFL said in a statement. “Case studies such as those compiled in this updated paper are important to further advancing the science and progress related to head trauma. The medical and scientific communities will benefit from this publication, and the NFL will continue to work with a wide range of experts to improve the health of current and former NFL athletes.”


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