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When one of the NFL’s top concussion specialists rejected the connection between football and chronic brain damage seven years ago, he set off a public uproar and was forced to step down.

Dr. Ira Casson, though, never abandoned his work.

Instead, Casson, a New York neurologist, led a team of other researchers in publishing a paper that concluded their study of retired NFL players had found little evidence of a link between pro football and chronic brain damage. Over the past two years, those findings have filtered through a series of scientific journals, cited repeatedly by other researchers, according to a STAT examination.


The problem, experts say: The study was deeply flawed.

At least eight researchers who have expertise ranging from imaging to neuropsychology and who reviewed the study at STAT’s request found problems with it. A few saw merits in the study, but most were less forgiving.


“It’s basically a waste of paper,” said Dennis Molfese, a professor at University of Nebraska, Lincoln, who until last year directed an intercollegiate concussion research group.

The publication of the 2014 study is more than a historical footnote. In February, Casson and others used the data to present similar findings in the American Journal of Sports Medicine. Findings from the study, meanwhile, have now been cited in at least nine other journal articles, including three written by a doctor who serves as a member of an NFL advisory committee.

The cascading effect could prove difficult to stop.

“Once a claim of truth, which in this case is a scientific paper, becomes part of the scientific record — if you will, the history of science — even when they have problems, it’s often difficult to expunge the historical record so it doesn’t have an impact on future studies,” said Eric Campbell, a Harvard Medical School professor of medicine.

Despite Casson’s skepticism, the scientific community for years has been accumulating evidence to support a connection between repetitive head trauma in football and negative health effects. In congressional testimony in March, the NFL’s senior vice president for health and safety acknowledged for the first time a connection between football-related head trauma and the neurodegenerative disease known as chronic traumatic encephalopathy, or CTE.

But science moves slowly, and rarely without dispute.

In an interview this week, Casson said he stood by his study.

He said it relied on the same methods as other “state-of-the-art studies at the time” and noted that the work was recognized as the “best original research paper” by the American Orthopaedic Society for Sports Medicine, which published the journal in which the paper appeared.

“This paper requires no defense,” he said.

A public firestorm

Casson, 67, long ago established a reputation for himself among concussion researchers. In the 1980s, he used emerging neuropsychological techniques and newly available CT-scanning technologies to identify chronic brain damage in boxers. He published his findings in JAMA in 1984.

“The boxing community wasn’t happy with me,” he recalled. Boxers and others sought counsel and treatment at his private practice in Queens, but he failed to attract funding for more formal research.

Then, in the early ’90s the NFL called.

With head-injury concerns starting to generate headlines, Paul Tagliabue, the league’s commissioner at the time, was forming a committee to examine the medical evidence surrounding concussions. Casson was recruited to join. And by 2007, he was appointed to lead it along with another researcher, David Viano.

With the league’s financial backing, the researchers began a study on the impact of head trauma on retired NFL players.

Their tenure, though, was short-lived.

Casson’s public statements — in which he asserted there was no evidence linking multiple head injuries to long-term neurological problems like depression, dementia, and early-onset Alzheimer’s in NFL players — drew an angry response. Critics derided him as “Dr. No.” And the NFL players union, which was negotiating a new contract at the time, called for his resignation.

In November 2009, he and Viano stepped down from the league panel.

“It was mutual,” Casson said of the decision to part ways with the league. Viano declined to comment for this story.

Testing for the study was stopped at the time. But the severing of the relationship with the NFL did not permanently end Casson’s research into head trauma in retired players. He dove back into his study, spending hundreds of hours on the project; Viano paid for some of the statistical analysis, and, Casson said, other researchers donated their time. Five years later, the team released their now-disputed paper.

“This paper requires no defense.”

Dr. Ira Casson

Published in the journal Sports Health, it presented the results of imaging, psychological, and cognitive tests performed on 45 retired NFL players, including neuropsychological exams Casson oversaw.

The paper concluded that “the majority” of players examined “had no clinical signs of chronic brain damage.”

The findings, in other words, were consistent with the view Casson had been espousing for years — and one that he and the other researchers acknowledged contradicted so much other scientific research.

“These results,” they wrote, “need to be reconciled with the prevailing view that a career in football frequently results in chronic brain damage.”

Ira Casson
Dr. Ira Casson, former co-chairman of the NFL’s concussion committee, speaks at a House hearing in January 2010. Bill Pugliano/Getty Images

‘Something bad was happening’

The data tell a far more complicated story, according to the experts who reviewed it at STAT’s request.

The study included a 29-page supplement with detailed breakdowns of the researchers’ findings, listing test results on the former NFL players who were studied. The results raised a number of red flags.

Dr. Samuel Gandy, associate director of the Mount Sinai Alzheimer’s Disease Research Center in New York, noted that roughly one-quarter had cognitive impairments. “I would not minimize that number,” he said.

Specialized MRI analysis used in the study also showed a connection between the number of concussions sustained by players and changes in brain function.

“This is a pretty strong finding that they state here in the supplement,” said Dr. Inga Koerte, a professor of neurobiological research who is studying the health of former NFL players. “But their conclusion is that they actually don’t find anything abnormal.”

“It’s fairly apparent that something bad was happening to these athletes,” said Tom Talavage, a neurotrauma researcher at Purdue University. “And they have very nicely danced around the subject.”

The study is “basically a waste of paper.”

Dennis Molfese, professor at University of Nebraska, Lincoln

Some experts cited methodological concerns. Most importantly, some researchers said, the study lacked a control group, which should have prevented the investigators from coming to any conclusions at all about the potential health impacts of playing football.

(Casson and his coauthors said in the study supplement they originally planned to include a control group of 60 athletes who played football in college, trained for the NFL, and played less than one season — and a total of 120 retired players — but the NFL pulled funding for the study following Casson’s and Viano’s resignation from the league’s concussion committee, which was later disbanded.)

Researchers also said the study’s participants may not have fairly represented the broader population of former NFL players. The authors tried to contact 5,000 by mail, and some by phone. Outside researchers say this method is likely to miss subjects with substantial cognitive impairments.

“Many demented subjects would not respond to mail and could misinterpret phone calls,” said Gandy, who has decades of experience as a clinician and researcher, mostly in the area of Alzheimer’s disease.

Casson said that view runs counter to his own observations with patients, and with boxers who participated in his earlier studies.

He also pointed out that two pages of the supplement are dedicated to discussing the ways in which the study group is and is not representative of NFL players.

[stat_brightcove id=”4664703562001″ credit=”Alex Hogan, Hyacinth Empinado/STAT” caption=”Concussions, or even more mild, repetitive head trauma, may lead to a degenerative brain disorder called chronic traumatic encephalopathy.”]

Still, the study group was too small for it to be representative, especially considering there’s an existing population of thousands of retired players, said Dr. Amy Borenstein, an emeritus professor at the University of South Florida College of Public Health.

“You could never convince anyone in my field that’s a representative sample,” Borenstein said. “I don’t care how many pages you spend talking about it, nobody’s going to believe it.”

Casson’s paper also concluded that the former players’ depression rates were in line with those of the general population, but cited no source for the statistics. The players’ depression rates were roughly double those of a similarly-aged group of men in the general population, according to government statistics.

The NFL declined to comment on this research, a league spokesperson said.

A passionate promoter

The findings from the 2014 study have now shown up in other papers.

A 2015 literature review coauthored by Gary Solomon, a professor at Vanderbilt University, cited the paper as concluding, “a career in the NFL was not causally related to later-life depression when compared to rates of depression in the general population.”

Solomon is also a consulting neuropsychologist for the Tennessee Titans, according to his website. He declined to comment.

The paper was mentioned in an article on the relationship between concussions and suicide on the website FiveThirtyEight. And another paper, published in Current Genetic Medicine Reports, said that the 2014 study “found no evidence of cognitive impairment” in the retired NFL players.

In an interview, a coauthor of the paper, Ramesh Raghupathi, a professor of neurobiology and anatomy at Drexel University College of Medicine, acknowledged the study may have been flawed but also said it had its merits.

“If the flaws weren’t there, this would be a stronger paper,” he said. “With the flaws, it weakens the paper, but not to the point of being disreputable.”

The study has been highlighted most passionately by the journal in which it originally appeared, which is edited by a doctor with ties to the NFL.

Dr. Edward Wojtys, the editor of Sports Health and a paid member of the NFL’s Injury and Safety Panel, has written three editorials citing the study, including one that characterized the results as “heartening.”

“One of the most comprehensive evaluations of living former NFL players has shown that they are probably not much different than the general population,” Wojtys wrote in an editorial published at the beginning of this year.

In an email to STAT in response to detailed questions, Wojtys reiterated that the research was “a well done thorough evaluation of former NFL players.”

In none of those editorials did Wojtys disclose his membership on the NFL committee. He said he has “never been involved in the design, implementation or analysis of NFL concussion research. That’s why I did not see a conflict of interest with the concussion editorial but do understand that some people might see one.”

The medical trade group that publishes Sports Health, the American Orthopaedic Society for Sports Medicine, also publishes the American Journal of Sports Medicine. In February, that journal published an article using the data from Casson’s 2014 study.

Of the journal articles that cited the original 2014 paper, only one was openly critical: a 2015 paper in the journal Brain Pathology coauthored by neuroscientists, some of whom, including Koerte, are also studying former NFL players.

Others in the neuroscience community said they would have published criticisms of their own, but for an important drawback. When a journal article is cited by another publication, it can increase the article’s perceived quality, thus improving the odds that the findings will be echoed elsewhere, or that the researchers will be rewarded with more funding on a topic.

Talavage, the neurotrauma researcher at Purdue University, said he considered writing a critique of Casson’s paper but decided against it. “It’s like, ‘There’s no such thing as bad publicity,’” he said. “It’s just as well that we not call attention to it.”