Sport on the brain; when do the risks outweigh the benefits?

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Written by Catherine Foster
Edited by Jonathan and Rachael 

You’re likely to have come across articles citing evidence that physical fitness and sport participation benefits cardiovascular and brain health1. Active lifestyles reduce the risk of high blood pressure, cardiovascular disease, Type 2 Diabetes, and stroke. Physical activity has also been shown to reduce inflammation, depression, cerebral metabolic and cognitive decline and brain atrophy.  The evidence is clear; sport is undeniably a good thing for your brain as well as your ability to fit in your jeans.

Yet, certain sports carry a relatively high risk of concussion, also misleadingly called mild traumatic brain injury (MTBI). American football, wrestling, soccer, ice hockey, boxing and rugby are among the sports with the highest risk of brain injury, though many others involve some risk. The point of this article is not to warn people off playing sport but to highlight the danger of mismanagement of concussion and the long-term effects of repeated impacts. Most research focuses on American Football but concussion is a frequent hazard in all contact and combat sports as well as equestrian and snow-sports.

In the US alone, the estimated annual incidence of sports-related concussions is around 3.8 million with approximately 50% going unreported2. Research and media attention has focused on concussion in American Football, partly due to the popularity of the sport. Another important factor was the diagnosis of chronic traumatic encephalopathy (CTE) by Dr. Bennet Omalu in 2002, in Mike Webster, a former star centre with a 14-year professional career. A form of dementia, CTE causes progressive brain degeneration resulting from an accumulation of the tau protein, which kills brain cells. CTE is now known to be caused by repeated brain trauma such as that suffered by athletes playing contact or collision sports3.

Bennet’s discovery, and ensuing battle with the National Football League (NFL) to have this disease risk acknowledged, was chronicled in the movie Concussion, starring Will Smith as Dr. Omalu. The movie followed the billion-dollar settlement the NFL made to retired players and families of ex-athletes for concealing the effects of repeated concussions. Around $10m of this was dedicated to research into concussion and CTE. Knowledge of the effects of concussion is much improved thanks to Dr. Omalu and others, and it is promising that a small portion of NFL profits will go towards further research. Ideally this would have been the NFL’s own initiative, but that is a separate argument. Increased awareness of concussion has increased reporting. Though, without a solution, the increasing size of players and aggression with which the sport is played is contributing to the rising number of concussions each year4.

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BENNET OMALU (LEFT) & WILL SMITH  WHO PORTRAYED HIM IN
THE 2016 FILM CONCUSSION.  IMAGE SOURCE


How regularly do concussions occur?

The NFL reported 271 concussions in the 2015 season, add this to college and school football and that is a lot of young adults with brain injuries.  It is estimated that a professional football player receives up to 1500 head impacts a season and a Virginia Tech study revealed that the G-force of these hits can reach 150 Gs5, with helmets only absorbing a fraction of the impact. Comparatively, fighter pilots experience a G-force of 9 during a jet roll. This seriousness of concussion is not limited to the NFL: helmetless sports such as soccer, where the impact speed of a ball headed by a player can be 70mph (40mph in children’s games), and rugby where a player’s average weight is around 114kg in the UK and higher internationally. In 2013-14 there were 86 reported concussions in English Rugby alone. So what actually happens to the brain following concussion and can anything be done to reduce the incidence?


What is happening to the brain?

Concussion’s principle causes are the acceleration and deceleration forces caused by a blow to the head or neck6. These forces cause the brain to rotate rapidly and the tissue to stretch and tear, resulting in the death of neuronal cell bodies, dendrites and axons, glia, and blood vessels in both grey matter and white matter connective tissue. Cells downstream of the site of injury are affected due to reduced energy supply or communication from other regions.

In addition, a metabolic cascade characterised by a huge release of neurotransmitters (chemical messengers) attempts to maintain balance following injury. This increase in activity increases glucose requirements and therefore hypermetabolism occurs, even though blood flow in the brain (which carries glucose) is reduced. This “energy crisis” in the brain typically results in a range of symptoms including dizziness or loss of consciousness, confusion, memory loss, headache and mood disturbances.

The good news is that with the correct care, symptoms of concussion typically subside within days or weeks thanks to the brain’s remarkable ability to repair itself, known as ‘brain plasticity’. Unfortunately, concussion is often not dealt with appropriately and individuals go on to develop post-concussion syndrome (PCS), a complex disorder involving physical disability, cognitive and mood disturbances. A second major risk is that of second impact syndrome (SIS) whereby a second injury occurs before the first has resolved. This injury may be extremely minor at first glance but rapidly advances to cerebral oedema, coma and is ultimately fatal.

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What can be done to reduce the incidence and consequences of concussion in sport?

As David Camarillo illustrates in his TED talk, current helmets do not adequately protect the brain and research is aimed at developing a more effective alternative. Senior sports clinicians including Dr. James Robson, Chief Medical Officer for Scotland Rugby Union, have called for changes in the way the game is played to reduce head injuries; it is estimated there is at least one concussion per game in the Six Nations alone. Changing the rules of a sport in a way that dramatically alters the game has huge financial and cultural implications but neuropathology and brain imaging studies have shown the impact of sports concussion on blood flow, metabolism and neurodegeneration in their current form7. Right now, the most effective way to reduce the risk of complications following concussion is to ensure that athletes refrain from playing for an appropriate time following any impact to the head. While it is unclear how many concussions it takes to cause irreversible damage, players and coaches should accept that if an individual continues to play after multiple concussions they are likely to develop neurological problems. One could argue that players should be educated on the risks and allowed to make their own decision on whether to participate in the sport. But, with high incidences of sports-related concussion in children and teenagers this argument becomes more complex and again boils down to; do the many benefits of sport, physical and cultural, outweigh the risks?

Header image source: Getty Images.

References

  1. Cotman, C. W., Berchtold, N. C., & Christie, L. A. (2007). Exercise builds brain health: key roles of growth factor cascades and inflammation. Trends in neurosciences30(9), 464-472.
  2.  Harmon, K. G., Drezner, J. A., Gammons, M., Guskiewicz, K. M., Halstead, M., Herring, S. A., … & Roberts, W. O. (2013). American Medical Society for Sports Medicine position statement: concussion in sport. British journal of sports medicine47(1), 15-26.
  3. Omalu, B., Bailes, J., Hamilton, R. L., Kamboh, M. I., Hammers, J., Case, M., & Robert Fitzsimmons, J. D. (2011). Emerging histomorphologic phenotypes of chronic traumatic encephalopathy in American athletes. Neurosurgery69(1), 173-183
  4. Haring, R. S., Canner, J. K., Asemota, A. O., George, B. P., Selvarajah, S., Haider, A. H., & Schneider, E. B. (2015). Trends in incidence and severity of sports-related traumatic brain injury (TBI) in the emergency department, 2006–2011. Brain injury29(7-8), 989-992.
  5. Jenkins, T., J. (2013). Sports Science Part II: Anatomy of a Hit in Football. Retrieved from: http://www.personal.psu.edu/afr3/blogs/siowfa13/2013/10/sports-science-part-ii-anatomy-of-a-hit-in-football.html
  6. McKee, A. C., Daneshvar, D. H., Alvarez, V. E., & Stein, T. D. (2014). The neuropathology of sport. Acta neuropathologica127(1), 29-51.
  7. Henry, L. C., Tremblay, S., & De Beaumont, L. (2016). Long-Term Effects of Sports Concussions Bridging the Neurocognitive Repercussions of the Injury with the Newest Neuroimaging Data. The Neuroscientist, 1073858416651034.
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