One of the most influential groups guiding doctors, trainers and sports leagues on concussions met last month to decide if it was time to recognize the link between repeated head hits and C.T.
Despite mounting evidence and a highly regarded U.S. government agency acknowledging the link, the group decided it wasn't. The leaders of the International Consensus Conference on Concussion in Sport said at their meeting in Amsterdam that they would continue to cast doubt on the link between head trauma and sports.
C.T.E., or chronic traumatic encephalopathy, was first identified in boxers in 1928 and burst into prominence in 2005, when scientists published their posthumous diagnosis of the disease.
Scientists have spent the past decade analyzing hundreds of brains from athletes and military veterans, and the variable visible in nearly every case of C.T.E. has been their exposure to repeated head trauma. There is a dose response between the severity of the C.T.E. and the number of years played.
In 2016 the N.F.L. acknowledged that there was a link between football and brain damage.
The leader of the final session of the conference dismissed the work of scientists who have documented C.T.E.
When you think about the human condition, it's crazy to think that there is one factor that is contributing to their current problems.
A recording of that session obtained by The New York Times, as well as interviews with people who attended, offered a rare glimpse of the fissures among the scientists who set concussion policy in sport.
Most of the group's dozen members agree on a consensus statement about concussions. Many of the world's top pro-sports leagues rely on it. The chief medical officers for the N.C.A.A. and World Rugby were involved in crafting that statement. The newest iteration was supposed to be out in 2023.
Conflicts of interest pose a challenge to the group's delay on accepting new research on concussions. The I.O.C., the F.I.A., and other governing organizations in sports sponsor the conference and provide them with research funding.
"This group has been led by people who don't really have a full understanding of the pathology of head injury at that level," said Willie Stewart, a neuropathologist in Glasgow who has diagnosed C.T.E. The conference leaders should be limited in how long they can stay. They don't have to worry about what they said four years ago because there should be a rotation.
The science was not settled on C.T.E., and that language has been adopted by sports leagues including the N.H.L., the N.C.A.A., and New Zealand Rugby.
Researchers pushing for a recognition of a cause-and-effect relationship between head trauma and C.T.E. were initially hopeful that the group's leaders would be swayed by new research. The leader of the group resigned after he was caught plagiarizing.
In conversations before and during the conference, leaders of the group centered their discussion on what was unknown about C.T.E., noting that it was unclear why some athletes got the disease and others who played the same sport didn't. It is not known how much head trauma is needed to diagnose C.T.E.
In the final session of the conference, titled "Long Term Sequellae and Criteria for Retirement," Iverson began by discussing the criteria the group would use to review concussions research.
The authors of the consensus statement did not include any of the major research papers on C.T.E.
Some research on C.T.E. that was not included in the formal review was still presented at the session. They weren't able to give specific details on which were included.
The limitations of the existing research were explained by Iverson. He said that most C.T.E. research only considered one or two variables, like age and sex, but not others.
Because the disease can only be diagnosed posthumously, scientists have not yet created long-term studies which follow living subjects through their lives. Scientists wouldn't know the results of the study until after the participants had died, so they needed to get the brains of people who weren't involved in collision sports.
These are some variables that are important to consider when thinking about brain health in later life.
Some people who attended the session were not convinced that the lack of research mitigated the studies that show a correlation between brain trauma and C.T.E.
It will take decades to do the types of studies they want to include in this way. We should not wait decades and have tens of thousands of people suffer from neurodegeneration when we could be doing something about it now.
A conference rule allows just 7 of the 29 writers to block language in the statement.
Cantu gave a 15-minute presentation in which he told the group that the issue of C.T.E. had been kicked down the road. The cognitive, behavioral and mood issues associated with C.T.E. make it hard to diagnose.
There have been more than 100 papers published on C.T.E. in the last two years, including one he co-authored with Chris Nowinski. He said that the paper helped convince the N.I.H. to change its mind.
The leaders of the conference were mocked by Nowinski and White as they arrived.
A parody of advertising in the 1940s and 1950s in which doctors promoted smoking appeared on their posters.
If they don't acknowledge a cause-and-effect relationship, more people are going to get hurt and it's going to ruin their reputation It will cost the organizers of the conference a lot of money if cause-and-effect is established.
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