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CTE found in 99 percent of former NFL players’ brains donated in new study

The study confirmed signs of CTE in 90 percent of the brains donated by former players at all levels of football.

Ken Stabler

A new study revealed that 99 percent of the brains former NFL players donated for research showed signs of chronic traumatic encephalopathy. The study, which was published Tuesday in the Journal of the American Medical Association, is the largest of its kind to date.

The sample size was small, with a total of 202 brains from men who played football at the high school, college, or professional level. Of those 202 brains, CTE was diagnosed in 177. The study acknowledges that there may be bias involved. Former players and their family members who donated brains for research likely means they noticed symptoms while their loved ones were still alive.

The flaws in the study are difficult to avoid, because doctors can’t currently diagnose CTE while a patient is alive. But the results still indicate a need for urgency at all levels of football about preventing CTE.

"There's no question that there's a problem in football. That people who play football are at risk for this disease," Dr. Ann McKee, the director of Boston University's CTE Center and the coauthor of this study, said via CNN. "And we urgently need to find answers for not just football players, but veterans and other individuals exposed to head trauma."

The rate of diagnosis varied depending on the level of football each person had played. It was most prevalent in former NFL players, with 110 of 111 showing signs of CTE. It was high among players who stuck with the sport through college, with 48 of 53 showing a confirmed diagnosis. Former high school players had the lowest rate, with just three of 14 confirmed with CTE.

What is CTE, and how is it diagnosed?

CTE is the result of repeated head trauma, and it’s most commonly diagnosed in veterans and people who have played contact sports, particularly American football.

The symptoms vary from person to person and can be mistaken for other conditions. This makes it more difficult to accurately diagnose. A person suffering from CTE could experience any combination of symptoms like confusion, memory loss, depression, impaired judgment, anxiety, anger issues, aggression, difficulty controlling impulses, and suicidal tendencies.

This study included the brains of some well-known former NFL players who were already confirmed to have CTE, including quarterback Ken Stabler and safety Dave Duerson.

The rate at which these former players’ brains were diagnosed with CTE is alarming, but not surprising. A previous study included the brains of 165 former players, and of those, 96 percent of the former NFL players’ brains showed signs of CTE.

CTE is caused by an abnormal buildup of tau proteins in the brain. These proteins essentially keep the flow of nutrients and cells in the brain on an orderly track. When the proteins build up, it creates roadblocks and deprives brain tissue of what it needs to stay healthy. A similar tau protein abnormality is connected to Alzheimer’s disease.

The amount of buildup and how it’s distributed determined the severity of the disease in each brain studied. Researchers classified four stages of the disease, with stage one as the least severe and stage four being the most severe.

Interestingly, the study found a correlation between the milder stages of the disease and significant behavioral and emotional symptoms during the person’s lifetime. That’s yet another indication that more research is needed about from CTE.

Where does the NFL go from here?

The league finally admitted in 2016 that there is a connection between football and CTE. It was a long time coming. Until that point, the NFL had mostly attempted to dodge responsibility despite significant evidence suggesting a strong link.

The league settled a landmark concussion lawsuit brought by former players in 2013, and after the settlement was finalized, the NFL acknowledged the link between football and CTE. The settlement didn’t provide any relief for players who will be diagnosed with CTE in the future.

The concussion protocol is the league’s primary approach to CTE prevention, but it’s flawed. Concussions affect everyone differently, and symptoms can show up days after the injury, which complicates things. The rules on the field are also designed to prevent head injury, but they’re not always consistently enforced.

The league has made advances in helmet technology, and some teams are adjusting to rugby-style tackling to lessen the risk of head injuries for players. But there’s no way for the NFL to make the game truly safe.

And concussions aren’t the only concern in CTE prevention. It’s the repeated hits players experience each week that can lead to CTE.

"As if the evidence we had linking football and CTE wasn't overwhelming enough already, we now have an expert neuropathologist, Dr. Ann McKee who found CTE in 110 out of 111 of the former NFL player brains she studied,” Representative Jan Schakowsky (D., Ill.), who is leading the charge against CTE in Congress, said Tuesday. “The time for denying facts and looking the other way is over.

“We must now actively seek out ways to protect the health and wellbeing of players from Pop Warner to the NFL and every league in between. It is also imperative to ensure that the American people are informed about the dangers associated with playing football."

The league released a statement Tuesday about the results of the new study, saying it is committed to supporting research into CTE and finding ways to prevent head injuries and effectively treat them.

"In 2016, the NFL pledged $100 million in support for independent medical research and engineering advancements in neuroscience related topics,” the statement read. “This is in addition to the $100 million that the NFL and its partners are already spending on medical and neuroscience research."

The New York Times published an interactive overview of the study’s results and pointed out that about 1,300 former NFL players have passed away since Boston University’s CTE Center began studying the condition. The link between football and CTE is clear.

So even if every one of the other 1,200 players would have tested negative — which even the heartiest skeptics would agree could not possibly be the case — the minimum C.T.E. prevalence would be close to 9 percent, vastly higher than in the general population.

There’s still much to learn about diagnosing, treating, and most importantly preventing CTE. The results of this study show that the need is pressing.