MICHEL MARTIN, HOST:
For years, as researchers learned more about the link between professional football and the degenerative brain disease known as CTE, one big question loomed - just how common is it among former NFL players?
STEVE INSKEEP, HOST:
A new study out this week puts a number on it. At least 25% of former pro players who died between 2016 and 2021 had CTE.
MARTIN: Joining us to tell us more about this is NPR's sports correspondent Becky Sullivan. Becky, good morning.
BECKY SULLIVAN, BYLINE: Hey. Good morning, Michel.
MARTIN: Twenty-five percent - I mean, that sounds like a really significant number.
SULLIVAN: Yeah. I mean, it is. And, in fact, I think it's - the sort of actual prevalence is likely to be higher because CTE can only be diagnosed at death, and so it's really only definitively been found in folks whose brains were donated to scientists or who asked for that kind of autopsy.
And so these researchers at Mass General Brigham, who put out this study this week, essentially they took a look at every brain that's been donated to this bank of samples that's held at Boston University, then they compared that to a list of every football player who had appeared in at least one NFL game since 1949, then they sort of narrowed the range down to those who had died between those years that we just heard - 2016 and 2021.
And so that 25% number - that quarter - is the percentage of players who had been definitively diagnosed by these researchers with CTE. And so the true number, they suggested, would be higher because there are some people with a CTE diagnosis outside of that brain bank, for example, and then also just plenty of suspected cases that weren't ever autopsied in this way.
MARTIN: Are there questions that the study does not answer?
SULLIVAN: Oh, many. Yeah, for sure. I mean, for one, I think it just doesn't put a hard number - right? - on this prevalence. That 25%, that's the minimum, yes, and then actually, at the sort of high end of the range - the extreme high end - they suggest that 98% could be the maximum. But that's obviously an extreme estimate because, you know, we know it's not a guarantee that professional football players will develop CTE because there are samples in the brain bank that were definitively cleared of it. And so the reality, obviously, is somewhere in the middle of that range.
I think the other important thing to point is that the average age of the brain donor cohort was 66 years old at death, meaning their professional football careers took place decades ago. The NFL, as you know, Michel, and the sport of football in general, has made a lot of changes since then. Helmets, for example, have gotten a lot more sophisticated in terms of protecting your brain. Dangerous tackles have been banned. Which is not to say that this problem has gone away. Football involves a lot of hits. But that 25%-plus number might not be true of players today. We just don't know.
MARTIN: Does this have implications for current and more recent NFL players?
SULLIVAN: Yeah. I mean, the researchers I spoke to, both involved with the study and not, really care about living players, and these headlines about CTE can be really scary for them because obviously this is a disease that is associated with some scary symptoms. And so here's Rachel Grashow. She is a neuroepidemiologist who helps run the Harvard Football Players Health Study. She was not involved in this new week's research, but here's how she put it.
RACHEL GRASHOW: So our concern is that the public and kitchen-table conversations around CTE are creating hopelessness in living former NFL players, and this hopelessness may discourage them from reaching out to their doctors and getting treated for conditions like sleep apnea that are causing worrisome symptoms.
SULLIVAN: The research here basically is just quite fuzzy on what symptoms are actually directly caused by CTE versus other conditions, and so players shouldn't hesitate to seek medical care. Don't assume it's CTE.
The NFL Players Association emailed players yesterday about this. You know, they said CTE might be significantly more common among players than they previously understood. The PA and the league itself both support research, but clearly this is a big deal and will be plenty talked about as we head into the season kicking off soon.
MARTIN: That is NPR's Becky Sullivan. Becky, thank you.
SULLIVAN: You're welcome. Transcript provided by NPR, Copyright NPR.
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