"I don’t think it’s been proven that the game of football causes CTE."

Larry Fedora on Wednesday, July 18th, 2018 in an interview

UNC football coach says it's not 'proven' football causes CTE

North Carolina head coach Larry Fedora walks the sidelines during the second half of Notre Dame's 33-10 victory over UNC at Kenan Stadium in Chapel Hill, NC Saturday, Oct. 7, 2017.

Football is under attack.

That’s what Larry Fedora, head coach of the UNC football team, told reporters during an ACC media event on July 18. Without naming anyone, Fedora said "people twist the data" on football-related injuries to argue that the game isn’t safe.

Football is safer than it has ever been, he said, adding that reports of the game’s ties to head injuries are overblown.

"I don’t think it’s been proven that the game of football causes CTE," Fedora said.

CTE is short for chronic traumatic encephalopathy, a progressive degenerative brain disease linked to head trauma.

"Now we do know, from my understanding, that repeated blows to the head causes it," Fedora said. "So I’m assuming, every sport that you have, football included, could be a problem with that. As long as you’ve got any kind of contact, you can have that."

Fedora is right about CTE being caused by blows to the head. But is he right that researchers haven’t "proven" that football causes CTE?

Through a spokeswoman, he declined PolitiFact’s request to elaborate on his claim. But PolitiFact found that Fedora’s point is somewhat valid.

Scientists have suspected a link between football and brain problems for decades. However, research into the whether the sport consistently causes CTE hasn’t gotten very far.

110 of 111 brains

CTE cannot be diagnosed in someone until they die, so it’s impossible at this point for doctors and scientists to measure football’s effect on the human brain on a year-to-year basis. The most illuminating information emerged in 2017.

That year, the Journal of the American Medical Association published the work of researchers who studied the brains of deceased football players who played at various levels, from high school to college to semi-pro and the NFL.

In total, nearly 88 percent of the brains — 177 of 202 — submitted for the research tested positive for CTE. But the rate of CTE was lower in younger players. (NPR summarized the research.)

▪ Of the 14 players who played only in high school, just three had CTE.

▪ Of the 53 players who stopped playing after college, 48 had CTE.

▪ Of the 22 players who played in the Canadian Football League or a semi-pro league, 16 had CTE.

▪ Of the 111 players who played in the NFL, 110 had CTE.

(An NFL player may have a higher risk of CTE if he began playing as a child. A separate study, published in 2014, found that former NFL players who started playing football before age 12 fared worse on cognitive assessments than players who started in their teens, as Vox explained this year.)

Dr. Ann McKee, one of the researchers who conducted the 2017 study published in JAMA, said those results show a link between football and CTE.

"We’re seeing this (CTE) in a very large number that participated in football for many years. So while we don’t know the exact risk and we don’t know the exact number, we know this is a problem in football," she told NPR.

But each of the brains was donated, leaving some researchers divided on how to characterize football’s ties to CTE.

Sampling bias

Dr. Peter Cummings, forensic pathologist and a neuropathologist at Boston University School of Medicine, wrote in a 2017 Yahoo Sports column that McKee’s study doesn’t definitively prove a link between football and CTE. He noted the brains were donated by families who likely suspected the player had developed neurological problems.

"Because of this sampling bias, we cannot estimate the prevalence or incidence of CTE (meaning the total number of cases and the number of new cases expected each year in football players); nor can we establish risk or a cause-effect relationship between head injury and development of CTE," Cummings wrote.

"To do that you need a randomly selected population comprised of people with the disease and people without the disease," he said. "In other words, we do not have a complete picture of what causes CTE, how common CTE is, or what the chance of getting CTE may be for anyone, or even what symptoms, if any, CTE causes."

Another recent Yahoo Sports column quotes Cummings defending Fedora, saying that "association is not causation." The same column refers to CTE researchers in Canada, who warn that the most commonly cited studies on the disease "do not allow for the collection of any epidemiological data and are not representative of the general population."

The studies are "limited by methodological biases, pathological inconsistencies, insufficient clinical data, and a reliance on inherently biased postmortem data," their abstract says.

The burden of proof

Lewis Margolis, a pediatrician and epidemiologist at the University of North Carolina’s Gillings School of Global Public Health, said he generally agrees with Cummings and others that the scientific proof has yet to be determined.

"Has there been a double-blind, placebo-controlled trial where some boys are exposed to brain trauma and other boys are not and then later examined for CTE? The answer is no," Margolis said in an email. "Such a trial would not be ethical."

UNC has a research center dedicated to studying the link between contact sports and head injuries. Its research shows a clear relationship between football and brain trauma, Margolis said.

"The implication of the statement by Fedora is that because we do not have the definitive (randomized controlled trial) for CTE we cannot say that football causes CTE. To me this misses that point that football increases the risk of head trauma/concussions with known consequences, even if there is not a definitive link (yet) to CTE," he said.

Margolis has warned that players or parents who are waiting for definitive, scientific proof could be putting themselves or their kids at risk.

"The tobacco industry used to say that the relationship between smoking and lung cancer was ‘merely’ a statistical association, similar to saying that there is not proof that football causes CTE," Margolis said. "The weight of the evidence against tobacco eventually tipped the scales, absent randomized trials, and I think the weight of the evidence of the harms of football is similar, even without a definitive link to CTE."

NFL acknowledgment

Back to Cummings and the lack of a valid scientific study proving that football causes CTE. The NFL, which has been accused of suppressing information about how the sport affects players’ long-term health, could use the same argument.

And, for a while, it did. ("Frontline" in 2013 published a timeline showing key events and research dating back to 1994.)

In 2013, while admitting no wrongdoing, the NFL reached a $765 million settlement with former players after 4,500 of them sued the NFL on the basis that the league minimized the risk of concussions. (Amid a challenge, the settlement was later upheld by the U.S. Supreme Court.)

Then in March 2016, for the first time, the NFL publicly acknowledged a link between football and CTE. The statement came while Jeff Miller, the NFL’s senior vice president of health and safety policy, was part of a round-table discussion with the U.S. House Committee on Energy and Commerce.

Miller pointed to McKee’s work as evidence. And the NFL released a statement the day after Miller’s claim, saying his comments "accurately reflect the view of the NFL."

Our rating

Fedora said it hasn’t been "proven that the game of football causes CTE." He’s right that there hasn’t been a controlled study showing, conclusively, that playing football directly causes CTE.

However, studies have shown CTE in the brains of more than 100 former football players, and the NFL has acknowledged a link between football and CTE. There’s enough evidence to show a connection between football and CTE. We rate this claim Half True.