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Sports industry may have helped downplay dangers of concussions and head injuries

Fresh doubt has been cast over the sports industry’s influence on concussion and head injury research, and stirred up old allegations that sporting bodies and prominent researchers have underplayed the risk sportspeople run of developing an incurable condition called chronic traumatic encephalopathy, with symptoms similar to Alzheimer’s disease.

While the Concussion in Sports Group (CSG) will, in May, release new guidelines and safety rules related to head injuries, tackling rules in some types of rugby are already changing, and recent research has also warned of the dangers of paediatric concussions, specifically when followed by migraines, writes Zano Kunene for Bhekisisa.

The CISG is funded by the IOC, Fifa, World Rugby, the FEI (the International Federation for Equestrian Sports), the FIA and the International Ice Hockey Federation, and shapes concussion policy across elite and grassroots sport.

Five counts of plagiarism, 10 retracted scientific papers and red flags about 74 more articles because of publication misconduct were the basis of a huge shake-up in sports science that led to the allegations about scientists downplaying the danger of head injuries for professional athletes over time.

At the centre is Paul McCrory, former editor of the British Journal of Sports Medicine (BJSM) between 2001 and 2008, during which time which he published many opinion pieces and editorials, including views on whether a blow to the head should mean keeping an athlete off the field.

In one of the retracted pieces, from 2001, McCrory misquoted an extract from a 1952 article on concussion in sport, which he then used to argue that recommendations for when a player can return to sport are based on “an arbitrary exclusion period”.

This dealt a blow to the reputation of the CISG, which compiles best practice rules for dealing with head injuries in sport. McCrory is a founding member of this body and was lead author on their 2017 consensus statement (although the investigation into McCrory’s publication misconduct does not directly link to the group’s recommendations).

McCrory resigned from the CISG in March 2022. He did not respond to Bhekisisa’s requests for comment.

Criticism and chronic brain injury

Jon Patricios, a South African sports medicine physician who co-leads the CISG’s scientific team, and who is the main author on the group’s newest consensus statement (to be released in May), says the claims made against McCrory haven’t affected the rigour with which the CISG considered its views when compiling the set of recommendations.

But there have been changes to how the CISG is structured since the previous consensus statement, published in 2017. This was to ensure its review methods are robust and to address claims that sporting bodies have too much influence over the scientific process, as a group of 17 researchers and public health advocates wrote in a letter in the Journal of Law, Medicine and Ethics in 2021.

A crucial criticism in their letter is that the CISG has consistently underplayed growing evidence that repeated hits to the head can lead to chronic traumatic encephalopathy (CTE), an untreatable neurodegenerative brain disorder, meaning brain cells die or stop working, worsening over time. Symptoms include memory loss, impaired judgment and personality changes, like violent behaviour.

However, there aren’t any tests for CTE other than examining brain tissue after death, so it can’t be diagnosed while someone is alive. In a case where a diagnosis of CTE is confirmed, a pathologist would see an unusual build-up of a specific type of protein in the brain, which affects how well nerve cells work.

The CISG has been one of the main opponents of a causal link between repeated concussions and someone developing CTE.

Yet major public health agencies, likes the US Centres for Disease Control & Prevention and the National Institute for Neurological Disorders and Strokes acknowledge that CTE is “caused in part by repeated traumatic brain injuries” and the authors of the 2021 critique warned that the CISG’s 2017 statement is incomplete.

But in a study published in June last year, a group of researchers led by Chris Nowinksi of the Concussion Legacy Foundation concluded that repeated hits to the head do cause CTE.

How does CTE work?

In a healthy brain, so-called tau proteins help to keep the structure of nerve cells intact. But when there’s a build-up of these proteins in the brain, they tangle together and prevent nerve cells from communicating with each other. This can affect a person’s ability to think and remember things, as often happens in Alzheimer’s disease or dementia.

Although hard blows to the head could lead to abnormal tau protein build-up, other factors, like genetics, could also contribute.

Scientists also caution that there is little conclusive evidence on how common CTE is, how many head impacts can lead to the disease and that the connection between what a brain looks like and how it functions is not clear.

“Not everyone, even with the worst forms of repetitive impact (such as boxing), develops a neurodegenerative disease. And that’s what makes the understanding quite murky,” Anthony Figaji, who heads up paediatric neurosurgery at the University of Cape Town, told Bhekisisa. He’s also the National Research Foundation’s chair on clinical neuroscience.

Plus, some of the symptoms of CTE, like mood disorders (for example, depression), behavioural difficulties like suicidal thoughts or substance abuse, and impaired thinking or memory are commonly found in the general population, too.

New info from the CISG

For the first time, the CISG will now include discussions on what kind of head injury is bad enough for a player to retire from collision sports, like rugby, in their upcoming consensus statement, Patricios said.

The potential long-term effects, including CTE, is also one of 10 topics for which the group is reviewing new evidence, he added.

More experts were brought in to evaluate research on the condition, including some of Nowinski’s co-authors, but Patricios wouldn’t say whether the Nowinski study was included in the CISG’s official review.

Why is the Nowinski study a bombshell?

Nowinski and his team showed, from analysing more than 100 studies, that the existing research on CTE meets all nine of Bradford Hill’s criteria for causation. This method is used in public health issues to help epidemiologists figure out if there’s a strong enough link between two occurrences to conclude that one thing directly leads to the other.

It’s a valuable method to use when there are environmental factors at play, the authors say.

The Nowinski paper claims that the methodology the CISG uses to evaluate evidence (called the Oxford Levels of Evidence) doesn’t catch environmental issues well enough because the method was designed for a clinical setting.

Hill’s approach has also been criticised, though, for being outdated, bringing into question whether it’s still a good way to make decisions in public health.

The Nowinski paper argues that diseases caused by environmental factors can be prevented, or made less dangerous. Their conclusion also poses a legal quagmire: children who participate in school sports are too young to consent to taking on the long-term risks of developing CTE.

But Figaji cautions that the study might not apply to the general population because it relied on brains that were donated to a brain bank for a specific medical reason (and thus are already more likely to have had signs of CTE), leading to a potential bias.

What does this say about rugby’s future?

The Nowinski study recommends rule changes around tackling and heading in children’s sports, as they are more prone to experiencing traumatic brain injuries. These include suggestions for limiting subconcussive blows (head bumps that don’t qualify as causing concussion) by, for example, banning heading the ball in youth football until the age of 14.

It also calls for players at professional levels to be told about the risk of CTE so they can participate knowing what they sign up for.

Patricios agreed it would be important to educate people on the risk of CTE when they decide to play a sport like rugby, but he said it’s hard to help people make informed decisions without information about exactly how many head impacts would result in the condition.

Figaji says that until there is definitive research and ways to detect tau protein build-up that occurs exclusively in CTE, it could be too early to make big changes to sporting rules.

However, being cautious, especially with children’s sport, is warranted “because there’s much we don’t know”. In general, he says, head injuries should be avoided. “But what qualifies as an injury, even a mild one, remains unclear.”

Meanwhile, Canadian research has found that children suffering from migraines after concussion are more likely to suffer prolonged symptoms of the injury than those with other forms of headache or no headaches at all.

“Early assessment of headache – and whether it has migraine features – after concussion help predict which children are at risk for poor outcomes and identify those needing targeted intervention,” said senior author Keith Yeates, the Ronald and Irene Ward Chair in Paediatric Brain Injury Professor and head of the Department of Psychology at the University of Calgary, Alberta.

About 840 000 children a year visit an emergency department in the US after having a traumatic brain injury, with as many as 90% of those visits involving a concussion. Although most children recover quickly, at least one-third continue to report symptoms a month later, reports Medscape.

Post-traumatic headache occurs in up to 90% of children, most commonly with features of migraine, found the researchers.

Their study, published in JAMA Network Open, was a secondary analysis of the Advancing Concussion Assessment in Paediatrics (A-CAP) prospective cohort study. it was conducted at five emergency departments in Canada from September 2016 to July 2019 and included children and adolescents aged eight to 17 who presented with acute concussion or an orthopaedic injury.

Children were included in the concussion group if they had a history of blunt head trauma resulting in at least one of three criteria consistent with the World Health Organisation definition of mild traumatic brain injury. The criteria include loss of consciousness for less than 30 minutes, a Glasgow Coma Scale score of 13 or 14, or at least one acute sign or symptom of concussion, as noted by emergency clinicians.

They were excluded from the concussion group if they had deteriorating neurologic status, underwent neurosurgical intervention, had post-traumatic amnesia that lasted more than 24 hours, or had a score higher than four on the Abbreviated Injury Scale (AIS).

The orthopaedic injury group included patients without symptoms of concussion and with blunt trauma associated with an AIS 13 score of four or less.

Patients were excluded from both groups if they had an overnight hospitalisation for traumatic brain injury, a concussion within the past three months, or a neurodevelopmental disorder.

The researchers analysed data from 928 children of 967 enrolled in the study. The median age was 12.2 years, and 41.3% were female. The final study cohort included 239 with orthopaedic injuries but no headache, 160 children with a concussion and no headache, 134 with a concussion and non-migraine headaches, and 254 with a concussion and migraine headaches.

Children with post-traumatic migraines 10 days after a concussion had the most severe symptoms and worst quality of life three months after their head trauma, the researchers found.

Children without headaches within 10 days after concussion had the best three-month outcomes, comparable to those with orthopaedic injuries alone.

The researchers said the strengths of their study included its large population and its inclusion of various causes of head trauma, not just sports-related concussions. Limitations included self-reports of headaches instead of a physician diagnosis and lack of control for clinical interventions that might have affected the outcomes.

Dr Charles Tator, director of the Canadian Concussion Centre at Toronto Western Hospital, said the findings were unsurprising.

“Headaches are the most common symptom after concussion,” Tator, who was not involved in the latest research, told Medscape. “In my practice and research with concussed kids aged 11 and up, and with adults, those with pre-concussion history of migraine are the most difficult to treat because their headaches don’t improve unless specific measures are taken.”

Tator, who is also a professor of neurosurgery at the University of Toronto, said clinicians who treat concussions must determine which type of headaches children are experiencing and refer them as early as possible for migraine prevention or treatment and medication, as warranted.

Study details

Association of Posttraumatic Headache With Symptom Burden After Concussion in Children

Jacqueline Josee van Ierssel,  Ken Tang,  Miriam Beauchamp, et al

Published in JAMA Network Open on 8 March 2023

Key Points

Question Is post-traumatic headache phenotype associated with symptom burden and quality of life three months after concussion among children aged 8 to 16 years?

Findings In this cohort study among 928 children with concussion or orthopaedic injury, children with post-traumatic migraine symptoms had higher symptom burden and lower quality of life 3 months after concussion than children with non-migraine headache. Children with no headache after concussion had the lowest symptom burden and highest quality of life following concussion, comparable with children with orthopaedic injury.

Meaning These findings suggest that post-acute headache phenotype was associated with symptom burden and quality of life three months after concussion.


Headache is the most common symptom after paediatric concussion.

To examine whether post-traumatic headache phenotype is associated with symptom burden and quality of life three months after concussion.

Design, Setting, and Participants
This was a secondary analysis of the Advancing Concussion Assessment in Paediatrics (A-CAP) prospective cohort study, conducted September 2016 to July 2019 at 5 Paediatric Emergency Research Canada (PERC) network emergency departments. Children aged 8.0-16.99 years presenting with acute (<48 hours) concussion or orthopaedic injury (OI) were included. Data were analysed from April to December 2022.

Post-traumatic headache was classified as migraine or non-migraine headache, or no headache, using modified International Classification of Headache Disorders, 3rd edition, diagnostic criteria based on self-reported symptoms collected within 10 days of injury.

Main Outcomes and Measures
Self-reported post-concussion symptoms and quality-of-life were measured at 3 months after concussion using the validated Health and Behaviour Inventory (HBI) and Paediatric Quality of Life Inventory–Version 4.0 (PedsQL-4.0). An initial multiple imputation approach was used to minimise potential biases due to missing data. Multivariable linear regression evaluated the association between headache phenotype and outcomes compared with the Predicting and Preventing Post-concussive Problems in Paediatrics (5P) clinical risk score and other covariates and confounders. Reliable change analyses examined clinical significance of findings.

Of 967 enrolled children, 928 (median [IQR] age, 12.2 [10.5 to 14.3] years; 383 [41.3%] female) were included in analyses. HBI total score (adjusted) was significantly higher for children with migraine than children without headache (estimated mean difference [EMD], 3.36; 95% CI, 1.13 to 5.60) and children with OI (EMD, 3.10; 95% CI, 0.75 to 6.62), but not children with non-migraine headache (EMD, 1.93; 95% CI, −0.33 to 4.19). Children with migraine were more likely to report reliable increases in total symptoms (odds ratio [OR], 2.13; 95% CI, 1.02 to 4.45) and somatic symptoms (OR, 2.70; 95% CI, 1.29 to 5.68) than those without headache. PedsQL-4.0 subscale scores were significantly lower for children with migraine than those without headache only for physical functioning (EMD, −4.67; 95% CI, −7.86 to −1.48).

Conclusions and Relevance
In this cohort study of children with concussion or OI, those with post-traumatic migraine symptoms after concussion had higher symptom burden and lower quality of life three months after injury than those with non-migraine headache. Children without post-traumatic headache reported the lowest symptom burden and highest quality of life, comparable with children with OI. Further research is warranted to determine effective treatment strategies that consider headache phenotype.

SPort related concussion PDF
Bradford Hill13-938163 (2)

Frontiers in Neurology article – Applying the Bradford Hill Criteria for Causation to Repetitive Head Impacts and Chronic Traumatic Encephalopathy (Open access)


JAMA Network Open article – Association of Posttraumatic Headache With Symptom Burden After Concussion in Children (Open access)


Medscape article – Migraine After Concussion Linked to Worse Outcomes (Open access)


Bhekisisa article – Will a shake-up in sports science change SA rugby? (Creative Commons Licence)


See more from MedicalBrief archives:


Retractions, plagiarism concerns over dozens of articles by concussion expert


BJSM issues statement on plagiarism by its former editor-in-chief


England rugby CEO says lawsuit threat over concussion can drive change


Brain-injured rugby players lodge class action against global unions









Physical activity 72 hours post-concussion is safe for children – PedCARE trial


Concussion: Aerobic exercise helps adolescent athletes recover faster


Concussion sufferers ‘twice as likely’ to develop brain diseases — App data


Migraine in children linked to anxiety, depression – Canadian meta-analysis






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