On 1/17/09, The Times Online published a news article entitled, Can football cause dementia?. American readers should note that the website is from London, where the word “football” means “soccer” in the U.S. The article contains a discussion on the medical risks associated with soccer including brain injury and dementia. In so doing, the following statement is made about a study published by Delaney et al. (2008):

“Even youngsters are at risk. A recent study in the British Journal of Sports Medicine looked at the risks of head injury among 268 adolescent football players. Dr Scott Delaney, research director of emergency medicine at the McGill University Health Centre in America, found that the risk of concussion was 2.65 times higher for players who did not wear protective headgear.”

The word concussion is synonymous with mild traumatic brain injury. When one attempts to define a clinical condition, the definition needs to include operational criteria such that one can clearly demonstrate how one does or does not meet the definitional standard. To date, there have been many attempts to do this. The most widely recognized and cited include those put forth by the American Congress of Rehabilitation Medicine (ACRM; Kay et al., 1993), the Center for Disease Control and Prevention (2003), the World Health Organization (Holm et al., 2005), the Defense and Veterans Brain Injury Center (2006), and the American Academy of Neurology (1997).

Although all of the definitions put forth by these organizations differ in some respects, they all share one common important feature – they either require the presence of an alteration of mental status or require the presence of an alternation of mental status if more strong indicators of brain injury are not observed (e.g., seizures per the CDC definition). An example is that the ACRM criteria states that the alteration of mental status criteria can be substituted by the presence of a focal neurological deficit (e.g., loss of vision not due to an eye injury). This is because a focal neurological symptom would be strongly indicative of brain injury. Likewise, an alteration of mental status can reasonably attributed to brain injury provided other causes have been ruled out such as a panicked state at the time of injury or alcohol intoxication. Unlike focal neurological symptoms, vague symptoms such as dizziness or headaches can be caused by many different factors and therefore should not be readily attributed to brain damage. Since it is not as easy to detect mental status change in infants (compared to adults) if there is not a loss of consciousness, the CDC allows for lethargy, irritability, and vomiting to count towards the definition of concussion with infants. However, irritability and vomiting are not counted towards the definition of concussion in adults.

In 2001, the Concussion in Sports Group (CISG; Aubry et al., 2002) met in Vienna and put forth a “definition” of concussion that reads as follows: ”Concussion is defined as a complex pathophysiological process affecting the brain, induced by traumatic biomechanical forces.” The CISG then goes on to describe some features of concussions, such as that they are typically associated with normal brain scans. The main way that the CISG definition differs from those of other organizations is that it is non-operational. That is, CISG only provides an abstract definition (i.e., complex pathophysiological process) with some descriptive features, but provides no clearly operationally defined way to show how a concussion definitively manifests. The CISG does describe some symptoms that indicate that a concussion should be suspected (emphasis by Aubry et al., 2002) such as headaches and dizziness or which may indicate (emphasis mine) that a concussion has taken place. However, these are all statements of possibility and therefore the presence of such symptoms does not define a concussion per the CISG guidelines.

With this information established, which definition of concussion appears the most robust? One that can be operationally defined or one that cannot be? Interestingly, Delaney et al. chose the CISG definition. In so doing, they did not describe in their article that the presence of such symptoms “may indicate” a concussion or would lead one to suspect a concussion. Rather, Delaney at el. state the following:

“The definition of concussion as put forth by the Concussion in Sport Group (CISG) was used as the basis for diagnosing concussions. They defined concussion as any alteration in cerebral function caused by a direct or indirect (rotational) force transmitted to the head resulting in one or more of the following acute signs or symptoms: a brief LOC, light-headedness, vertigo, cognitive/memory dysfunction, tinnitus, blurred vision, difficulty concentrating, amnesia, headache, nausea, vomiting, photophobia or balance disturbances.”

As demonstrated above, the statement is simply not accurate because the CISG never “defined” concussion in such a matter. The only definition provided was non-operational and the symptoms listed were only described as possibly concussive by CISG. The reason why this is so significant is that the criteria used by Delaney et al. are overly liberal. According to their criteria, merely having a headache after heading a ball equates to brain injury when the fact is that headaches can occur for many other reasons besides brain injury. As another example, blurry vision can be caused by an eye injury and does not mean a brain injury occurred. Further compounding the problem is that the researchers determined if subjects suffered a concussion by having them fill out an online computer survey, rather than requiring a physical examination of acute injury characteristics which would be far more accurate. One concern about this is that not everyone understands what loss of consciousness means, and so it is unclear how many subjects knew what this meant on the online survey. This is particularly a problem since all of the subjects in this study were between ages 12 and 17. The study also does not make it clear when the subjects completed the online survey. Did they complete it the day of injury or much later?

These issues are not raised to be personally critical of Delaney et al., but to caution readers to understand that an overly liberal criteria for brain injury was used and to view reports about the percent of patients who suffer brain injuries from soccer based on this study with great caution. MTBIFacts.com was partly established to improve research in the areas of MTBI and it is hoped that this article helps improve research methodologies in the future.

On 1/18/09, a correction was posted to the TimesOnlinewebsite. A response will be awaited. Click here to return to media watch.

REFERENCES

American Academy of Neurology (1997). Practice parameter: the management of concussion in sports (summary statement). Report of the Quality Standards Subcommittee. Neurology, 48, 581-85.

Aubry, M. (2002). Summary and Agreement Statement of the 1st International Symposium on Concussion in Sport, Vienna 2001. Clinical Journal of Sport Medicine, 12, 6–11

Centers for Disease Control and Injury Prevention (2003). Report to Congress on Mild Traumatic Brain Injury in the United States: Steps to Prevent a Serious Public Health Problem.

Defense and Veterans Brain Injury Center Working Group on the Acute Management of Mild Traumatic Brain Injury in Military Operational Settings: Clinical Practice Guidelines and Recommendations. Defense and Veterans Brain Injury Center. Washington, DC, December 22, 2006.

Holm, L. (2005). Summary of the WHO Collaborating Centre for Neurotrauma Task Force on Mild Traumatic Brain Injury. J Rehabil Med, 37, 137-41.

Kay T. (1993). Mild traumatic brain injury committee of the head injury interdisciplinary special interest group of the American Congress of Rehabilitation Medicine. Definition of mild traumatic brain injury. Journal of Head Trauma Rehabilitation 1993, 86–87.

Delaney, J.S. (2008). The effect of protective headgear on head injuries and concussions in adolescent football (soccer) players. British Journal of Sports Medicine, 42, 110-15.