Research has already established that the intense tackles and utter brute force that takes place in professional football puts players at risk of permanently damaging their brain, or developing CTE — Chronic Traumatic Encephalopathy. But new data from Boston University suggests that that risk might be much higher than previously thought. Of the 376 former NFL players who participated in their study, a whopping 345 have been diagnosed with CTE: over 90%.

Dr. Ann McKee, director of BU's CTE Center and chief of neuropathology at VA Boston Health Care System, joined GBH’S All Things Considered host Arun Rath to break down the study's revalations. What follows is a lightly edited transcript.

Arun Rath: I wouldn't have thought a study could have made things sound even worse about what we know about football and CTE, but it seems like that's what we get from this.

Ann McKee: Well, it's actually been this bad for quite some time. In 2017, we released the numbers on about one-third of this many NFL players, and we had 99% at that time. Now, we have 376 [players] total that we've evaluated and 345 with the disease.

I think part of this new data release was to let people know that the disease is not going away. We still need to do something about it, not just for the athletes that are participating in sports right now, but for the players who are living and suffering from the results of CTE.

Rath: Well, I'm glad you laid it out that way because I felt like a few years ago we had this "come to Jesus" moment as a country with football. When we were talking about these findings, people were saying, "Things had to change, football could not keep going on like this." But it has. Is that impression valid?

McKee: I think it's entirely valid. People are alarmed, and they're concerned, and then they tend to forget and go on as usual.

You know, it's been surprising to me. I've been working on this for 15 years. I saw in the beginning that if we had enough players with [the] disease that sports leagues and the public would come around. Although we've made a lot of headway in terms of parents understanding the risks of some of these sports, we have a long way to go.

Rath: Give us a sense of what CTE does to people.

McKee: So CTE is a neurodegeneration that, in almost all instances, is associated with repetitive head impacts or minor traumatic impacts to the head. They aren't just the concussions, that's what everybody talks about. The NFL has done a lot about concussion awareness and concussion management, but that's not the culprit.

The culprit is the many more minor hits that don't cause a concussion — what we call the non-concussive hits — that accumulate over time. A single football player may accumulate thousands of these over his playing career, and that's what our research has shown to be the trigger for CTE. It's a dose-response relationship. The longer you play, the more repetitive head impacts you have, the risk for CTE goes up. In fact, our work has shown that it doubles for every 2.6 years of playing football.

What's been really tough for me to swallow is that this is a disease I've seen in teenagers, I’ve seen it in 20-year-olds, 30-year-olds. It's characterized by the increased deposition of tau in the brain. The [protein] tau has a very specific distribution and a very specific composition of the tau fibrils. It's not [like] any other diseases, like Alzheimer's or anything else. It's very specific, and it occurs in players of all ages. Those players get behavioral and mood changes. They start to develop rage issues, aggression, impulsivity, depression, suicidality... As it continues to progress, they get cognitive impairment, memory lapses and even dementia.

So this is a devastating disorder, not just for the players who have it, but for their families who are destroyed by this disease.

Rath: I know that, at least among the parents that I know, the attitude towards football has changed. A lot of us, speaking for myself, wouldn't let our kids play football now. What advice would you give parents? Is that an extreme reaction?

McKee: I think that's a very, very enlightened reaction. I certainly would have that same reaction if my children were at the age where they were playing football.

The problem is that the level of education that's available to parents and coaches and players varies considerably across the country. In the Northeast, you may get much more education than what is available to someone in other parts of the country.

We need to educate parents and players that this is a disease that can be prevented. It can be prevented by allowing your children to play at an older age, because if they start later they just don’t have the number of years of play. They could play a different sport not associated with head trauma. They could adopt different coaching and practice guidelines, so they're not as exposed to head trauma if they decide they want to play football.

There are a lot of things that can be done that aren't being done — at least, they're not being done on an even basis throughout the country.

"Although we've made a lot of headway in terms of parents understanding the risks of some of these sports, we have a long way to go."
Ann McKee, director of BU’s CTE Center

Rath: Are there other things that, at the professional level, the NFL can do in terms of mitigating the risk, if not eliminating it?

McKee: The NFL has not addressed the risk at all. I mean, they've put on more games per season, which immediately puts the players more at risk. They are not attempting to quantitate in any way the number of hits an individual player receives in a season. They're not doing anything to monitor their brain health — which they could do, by baseline and then postseason evaluations. And they're turning the conversation to concussions, when concussions are not the major problem in football.