Historic Review of Repetitive Head Impacts and Chronic Traumatic Encephalopathy

Samantha C. Bureau, Michael E. Buckland, Maurice A. Curtis, Daniel H. Daneshvar, Richard L. M. Faull, Lea T. Grinberg, Elisa L. Hill-Yardin, Helen C. Murray, Alan J. Pearce, Catherine M. Suter, Adam J. White, Adam M. Finkel, and Robert C. Cantu
Two American football players falling mid-tackle

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with a history of repetitive head impacts (RHI). CTE was described in boxers as early as the 1920s and by the 1950s it was widely accepted that hits to the head caused some boxers to become “punch drunk.” However, the recent discovery of CTE in American and Australian-rules football, soccer, rugby, ice hockey, and other sports has resulted in renewed debate on whether the relationship between RHI and CTE is causal. Identifying the strength of the evidential relationship between CTE and RHI has implications for public health and medico-legal issues. From a public health perspective, environmentally caused diseases can be mitigated or prevented. Medico-legally, millions of children are exposed to RHI through sports participation; this demographic is too young to legally consent to any potential long-term risks associated with this exposure. To better understand the strength of evidence underlying the possible causal relationship between RHI and CTE, we examined the medical literature through the Bradford Hill criteria for causation. The Bradford Hill criteria, first proposed in 1965 by Sir Austin Bradford Hill, provide a framework to determine if one can justifiably move from an observed association to a verdict of causation. The Bradford Hill criteria include nine viewpoints by which to evaluate human epidemiologic evidence to determine if causation can be deduced: strength, consistency, specificity, temporality, biological gradient, plausibility, coherence, experiment, and analogy. We explored the question of causation by evaluating studies on CTE as it relates to RHI exposure. Through this lens, we found convincing evidence of a causal relationship between RHI and CTE, as well as an absence of evidence-based alternative explanations. By organizing the CTE literature through this framework, we hope to advance the global conversation on CTE mitigation efforts.

Posted on BrainLine February 13, 2023. Reviewed February 13, 2023.

Comments (1)

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I had a STBI at 12, RHI (12-15x) have been ignored to my concerns. I have read a bunch of research. The most striking comment I found at the end of a research finding was that : They must stop ignoring, as PCP's ,patients with these traumas. Easier to ignore than treat! Shameful that for 50 yrs no follow up or MRI. Did have CT after 48 yrs,but,we know that only a MRI HAS VALUE!