Questioning the Link Between Sports-Related Concussions and CTE

Peter Cummings MSc, MD
Uzma Samadani MD, PhD
Jason Chung

On Jan. 18, an article by Dr. Lee Goldstein of Boston University and colleagues in Brain, a leading neurological journal, was released and touted as proving the link between subconcussive hits to the head and chronic traumatic encephalopathy (CTE) (“Real risk of CTE comes from repeated hits to the head, study shows,” Feb. 4). That same day the CTE advocacy group — the Concussion Legacy Foundation — announced a national campaign called F14G Football to convert all under-14 football into flag football, thereby eliminating tackle football.

The message sent to assembled media and onlookers was that eliminating tackle football for youth is the key to safeguarding the brains and futures of America’s youth.

The truth is not so simple.

The scientific evidence linking youth casual sports play to brain injury, brain injury to CTE, and CTE to dementia is not strong. We believe that further scientific research and data are necessary for accurate risk-benefit analysis among policymakers for two reasons.

First, evidence-based science calls for research to be conducted under generally accepted principles. The case series presented by the Boston University group, primarily due to its ascertainment bias, is weaker than the evidentiary standard sufficient to demonstrate an association or causation and conflicts with pathologic findings in other studies.

CTE pathology in the brain has been shown by British pathologists to be present in approximately 12 percent of normal healthy aged people who died at an average age of 81 years (Ling et al. Acta Neuropathologica). The presence of CTE pathology in the brain on autopsy has not been shown to correlate with neurologic symptoms before death.

To be clear, CTE pathology could be present in a normal person.

Indeed, even Dr. Goldstein’s article was more measured than his press. His article speaks in terms of likelihoods and qualifiers in noting that “the causal mechanisms, temporal relationships, and contextual circumstances that link specific brain pathology to a particular antemortem insult are impossible to ascertain with certainty based solely on post-mortem neuropathology.”

There is a disconnect between the categorical rhetoric in media and news releases describing “concussion” research on the one hand, and the muddled and contentious scientific reality on the other. As noted by Dr. Goldstein’s own research, the pathology and link between head impacts and long-term neurological conditions such as CTE is still unclear, with questions of causation yet to be settled.

This is not to say that head impacts or injuries are desirable — far from it. But there is scientific ambiguity about the prevalence of CTE in the general population in comparison to professional athletes and also about the significance of its presence. In fact, after reviewing all available evidence, the consensus statement from the international conference on concussion in sports states:

“A cause-and-effect relationship has not yet been demonstrated between [CTE] and sport-related concussions or exposure to contact sports. As such, the notion that repeated concussion or subconcussive impacts cause CTE remains unknown.”

Nothing in Dr. Goldstein’s recent study changes this ambiguity, which brings us to our second point. Before enacting sweeping legislation or policy spurred by fears of CTE, policymakers must conduct a risk-benefit analysis based on a holistic survey of public health concerns.

American youth are currently more sedentary than ever before. Compelling evidence from multiple sources shows that organized sports offer youth a way off the couch and promote the adoption of an active lifestyle, thereby mitigating the risks of, among other conditions, obesity, high blood pressure, diabetes, depression, osteoporosis, cardiovascular disease, stroke, drug use, teen pregnancy and, ironically, dementia.

The uncomfortable truth is that tackle football is the number one participation sport among high schoolers in America; it is accessible to children with diverse physiology in ways that other sports are not, and greater public consultation should take place to see if participation rates would remain as high for alternatives to tackle football.

Three recently published major studies found no increased risk for later-in-life brain diseases in men who played high school football (Jannsen et al., Mayo Clinic Proceedings; Savica et al., Mayo Clinic Proceedings, Deshpande et al., Jama Neurology). One might also speculate that children who engage in football would seek other less organized risk-taking behaviors if football were not an option.

Setting legislation and public policy is already a tricky process and overstating the degree to which scientific consensus exists may lead to pyrrhic victories. What we seek to establish are meaningful and durable standards based on validated and replicated diagnostic criteria so that the public health response to head impacts and CTE are not emotive or political, but data-driven. The political winds being as fickle as they are, laws and policies enacted without such scientific support will be vulnerable to backlash from those with deep economic and cultural ties to contact sports such as tackle football, to rejection by the scientific community, and to general confusion and misunderstanding by the public.

In the drive to protect young brains, there are not just two sides. Not everyone is a moral crusader or an NFL stooge. No reasonable person, least of all the professionals signing this letter, want to see youth injured. But when arguing for intervention based on public health or scientific principles, the data must inform the recommendation.

Additional data is required to make a truly informed decision regarding banning of sports. What is desperately needed are 1) funding from federal and private sources to launch longitudinal, multicenter statistically sound studies, 2) consistent coordinated measures and standards, and 3) facilitation from either government or a consortia of concussion research centers.

Only then will we know whether the perceived neurological risks of tackle football outweigh the benefits. And only then can we more confidently say that we are acting in the public interest.

Jason Chung is senior researcher and attorney at New York University Sports and Society.

Peter Cummings MSc, MD is a forensic pathologist and neuropathologist and assistant professor of anatomy and neurobiology at the Boston University School of Medicine.

Uzma Samadani MD, PhD is an associate professor in neurosurgery at the University of Minnesota and Rockswold Kaplan endowed chair for traumatic brain injury at Hennepin County Medical Center.

This article is submitted on behalf of 26 brain injury experts in neurosurgery, neuropsychology, neurology, neuropathology and public policy at 23 universities and hospitals in the United States and Canada.

The additional signatories are:

Lili-Naz Hazrati, associate professor of neuropathology at the University of Toronto; clinician-scientist at the Hospital for Sick Children, Toronto.

John Leddy, professor of clinical orthopaedics and rehabilitation sciences at the SUNY Buffalo Jacobs School of Medicine and Biomedical Sciences.

Barry Willer, professor in the Department of Psychiatry at the SUNY Buffalo Jacobs School of Medicine and Biomedical Sciences.

Rocco Armonda, president of ThinkFirst, a brain injury prevention foundation; director, neuroendovascular surgery and neurotrauma, and co-director, neurocritical care; professor of neurosurgery, Georgetown University Hospital and Washington Hospital Center.

Jason H. Huang, chair, Department of Neurosurgery at Baylor Scott and White Medical Center in Temple, Texas, and professor of surgery at Texas A&M University College of Medicine.

Kenneth Blumenfeld, adjunct clinical faculty, Department of Neurosurgery at the University of California, San Francisco; immediate past president of the California Association of Neurologic Surgeons; AANS delegate to the AMA.

Richard B. Rodgers, assistant professor of clinical neurosurgery and director of neurotrauma at the Indiana University School of Medicine.

James MacDonald, clinical associate professor of pediatrics and family medicine at the Ohio State University College of Medicine, Division of Sports Medicine, Nationwide Children’s Hospital.

Michael W. Kirkwood, founder and co-director of the Children’s Hospital Colorado Concussion Program and associate clinical professor of Physical Medicine and Rehabilitation at the University of Colorado School of Medicine.

David R. Howell, lead researcher for the Sports Medicine Center at Children’s Hospital Colorado and assistant professor of orthopedics at the University of Colorado School of Medicine.

Gary S. Solomon, professor of neurological surgery, associate professor of orthopedic surgery and rehabilitation and psychiatry and behavioral sciences; co-director, Vanderbilt Sports Concussion Center at the Vanderbilt University School of Medicine.

Mark E. Halstead, associate professor of pediatrics and orthopedics at Washington University in St Louis and director of the Sports Concussion Clinic at St Louis Children’s Hospital.

Francis X. Shen, associate professor of law at the University of Minnesota and senior fellow in law and neuroscience at the Harvard Massachusetts General Hospital Center for Law, Brain and Behavior and the Harvard Law School Petrie-Flom Center.

Mark Herceg, director of the Center for Brain Health and the Center for Concussion at Gaylord Specialty Healthcare in Wallingford, Conn.

William B. Barr, director of the neuropsychology division, Department of Neurology, at New York University Langone Health.

Arthur Maerlender, associate research professor and director of clinical research, Center for Brain, Biology and Behavior at the University of Nebraska-Lincoln; research director for the Big Ten-Ivy League Traumatic Brain Injury Research Collaboration.

Mayumi Prins, professor, UCLA Department of Neurosurgery and Brain Injury Research Center and associate director of the UCLA Steve Tisch BrainSPORT program.

Gregory Murad, associate professor and residency program director at the University of Florida Lillian S. Wells Department of Neurosurgery.

Peter Le Roux, neurosurgeon at the Brain and Spine Center at the Lankenau Medical Center in Pennsylvania.

Vernon B. Williams, director, Center for Sports Neurology and Pain Medicine at the Kerlan-Jobe Orthopaedic Clinic, an affiliate of Cedars-Sinai.

Michael G. Fehlings, professor of neurosurgery and vice chair of research, Department of Surgery, Halbert Chair in Neural Repair and Regeneration, co-chairman of spinal program, University of Toronto, Head Spinal Program; senior scientist, McEwen Centre for Regenerative Medicine, Toronto Western Hospital, University Health Network.

P. David Adelson, director, Barrow Neurological Institute at Phoenix Children’s Hospital, Diane and Bruce Halle Endowed Chair in Pediatric Neurosciences; chief, pediatric neurosurgery.

Shelly Timmons, neurosurgeon and professor, Department of Neurosurgery; vice chair, administration, and director of neurotrauma at the Pennsylvania State University Milton S. Hershey Medical Center; president, American Association of Neurological Surgeons.

9 replies »

  1. If it were up to me, I would probably ban tackle football before age 12 and substitute flag football instead. At the high school level and beyond, however, I have no problem with parents letting their kids play if the kids want to play as long as both fully understand the potential risks.

    Football is a popular sport. Kids learn to compete and be part of a team. Our school district has always had a strong football program. We have quite a few talented athletes many of whom come from low income, minority families. For many of these student athletes, a football scholarship makes it possible for them to go to college which their families couldn’t otherwise afford without burdening themselves and their child with crushing debt.

    At the college level, the largest and most famous football programs bring in enough revenue to pay for the school’s entire athletic program, including women’s sports, and then some. At smaller second and third tier colleges, many of the students they are able to attract would not have come if the school didn’t have a commitment to sports including football. Without sports, many of these schools would probably have to close.

    While severe football injuries are obviously tragic, so are injuries caused by car and motorcycle accidents. We can’t make life risk-free and we shouldn’t try to. We should provide sufficient information so people can make rational and fully informed decisions and respect the decisions they make whether we agree with them or not.

  2. Jason, thank you for calling this debate what it is: a public health issue. I would not summarize my experience with head injury in children as “feelings” but I suppose one head injured patient/ week over the last 18 years could be considered a matter of perspective.
    If you believe studies to be statement of “facts” then you are mistaken. Studies allow for sharing of informed opinions and “feelings” based on interpretation of collected (often biased) data. I am not advocating a total ban on participation — I am suggesting we should be cautious about participation in tackle football for those who have not reached physical maturity (or in fact neurological maturity — which is mid-20s age group.) This is the most responsible approach for those of us in the medical community until science can more definitively answer the question as to long term impact of trauma on developing minds.
    Ironically, policy making has been done ie value based care, when far less data is available. After all, it appears few policy makers are capable of understanding such complicated subjects as science and medicine. Do you really think they can grasp such a nuanced concept as CTE and head trauma? Doubtful.

  3. Niran,

    It’s a fact that football is the #1 rated sport in the US in terms of popularity and even high school participation. You can’t just substitute football for another sport and assume it’ll be a like-for-like in terms of getting kids to participate – football, no matter, how you feel, still is king in many corners of the country.

    As for your point about second impact syndrome, I’m not sure what your takeaway is here. We wrote an article calling for a rational discussion about the science behind CTE, long-term degenerative neurological effects and how it’s presented. I’m sure that dealing with traumatic head impacts and their consequences in other contexts such as SIS or post-concussion syndrome is sobering but that’s beyond the scope of what we addressed.

    I also think it’s important to note that we’re all on the same side of helping children. The signatories simply believe that the benefits of playing football should be weighed against known and verified risks based in quality science. This is a point that has been reiterated by your peers at the American Academy of Pediatricians as well (https://www.aap.org/en-us/about-the-aap/aap-press-room/pages/youth-football-injuries.aspx).

    I understand that you may have serious ethical questions about the consequences of allowing youth tackle football. And that’s a valid concern to have based on your ethical concerns. But does no good to anyone to enact laws and policies – particularly extreme ones such as implementing total bans – by overstating scientific consensus. Simply put, that’s misleading the public on the facts to get your way and it’s a problem that plagues all levels of policymaking in America.

    Finally, I’d point out that simply raising points doesn’t equate stumping for a side. We have to get out of the “everything is debate” mentality and prioritize public health issues based on facts, not feelings.


  4. Did you know that running, tennis, golf, and basketball also offer “a way off the couch”? I could write an exhaustive list that does not include football or lacrosse.
    My opinion will not be a popular one, but I must comment. We are talking about innocent CHILDREN. Not one individual who signed this letter is even a pediatrician. Every single signature is either from a surgeon (who makes money off operating on sports injuries), a neurosurgeon, a PhD academic, or neuropathologist, etc…oh and one Family doc, who is not a pediatrician either.
    Have any of you cared for a 16 year old boy permanently damaged from second-impact syndrome? Have you walked into his hospital room every day and reminded him of where he is, what happened, and witnessed the fear on his face? Would any of you let your children play football after sustaining one concussion?
    My job, and that of thousands of other pediatricians across this nation, is to ensure the safety and health of children from birth through adulthood. I have no conflicts of interest, make very little off of medical care from sports injuries or its’ associated long-term damage.
    I do acknowledge your point to be cautious when interpreting scientific data, however, encouraging parents to continue participating in tackle football when I have seen the damage, is absolutely unethical. Why don’t you all concentrate on something worthwhile, like how to rehabilitate these damaged children after multiple episodes of head trauma rather than stumping for the NFL.

  5. Hi William,

    Thanks for your thoughts. Your concerns about case studies were raised by the medical signatories as well. Definitely requires more thought and study.

    Thank you for reading the article!


  6. John, Peter,

    As I mentioned on Twitter, I’m not pro-NFL in any way. Head impacts should be minimized.

    Instead, I’m urging caution at conflating NFL issues with public health issues. According to many researchers, we still don’t have enough information about the pathology of CTE and its prevalence in the general population in order to determine whether it should be a definitive reason to ban popular activities like youth tackle football.

    My worry, as with my colleagues, is that we’re propagating science and its effects by how it sounds and feels rather than its true impact/risk to the population. We really need to address the problems caused by single-issue advocacy and its effect on public health and scientific literacy in this country.

  7. Jason,

    Knowing you, I doubt it. Given responses like the above. Think it’s super important that you make it clear that you are not “pro-NFL” but rather worried about the impact of how the science is being done here.

    My sense is that this is a much more complicated thing that it appears at first …

    It’s possible to be concerned about kids welfare and ask questions about how the science is being done at the same time. If we go around assessing every research study by it’s political acceptability, we’re going to quickly run into problems ..

    Oh, wait ..

  8. Article sounds like it was written by the NFL. Does not flag football offer, “a way off the couch and promote the adoption of an active lifestyle, thereby mitigating the risks of, among other conditions, obesity, high blood pressure, diabetes, depression, osteoporosis, cardiovascular disease, stroke, drug use, teen pregnancy and, ironically, dementia.”?

    Many sports offer all of the above without the risk of brain injury. It’s just America’s obsession with contact football that prevents the prudent change necessary to protect kids.

    “Only then will we know whether the perceived neurological risks of tackle football outweigh the benefits.”

    Whose kids are we going to use as the risk side of this study?

  9. That Ling et al cite in Acta Neuropathological was interesting but there were only four patients. I think there needs to be more support for these path findings and also it would be great if we could find an acute phase protein in CSF that would prove immediate inflammation or damage in neural tissue after a head injury. And then try to correlate this with future dementia, etc. Lots of work to do. There might be one of these that is a small enough molecule to escape the blood-brain barrier and be found in the peripheral blood. But it would have to be specific to central neural system damage. CRP would not do.

    I visualize these injuries as neurons, astrocytes, microglia, axons, dendrites, vessels having a slightly higher density than myelin and CSF. It is like BBs in jello. Therefore a sudden acceleration or deceleration of the entire brain causes these cells–that have a higher inertia and specific gravity–to move at a different speed from their surroundings and accordingly stretches and probably tears their cell processes and extensions, axons, synapses, etc., from more fixed structures like vessels, arachnoid, pia, dura or septa.

    But good stuff. Thanks for a fine article.