Chronic Neurophysiological Effects of Repeated Head Trauma in Retired Australian Male Sport Athletes

Pearce, Alan J.; Kidgell, Dawson; Tommerdahl, Mark; Frazer, Ashlyn K.; Rist, Billymo; Mobbs, Rowena; Batchelor, Jennifer; Buckland, Michael E.

doi:10.3389/fneur.2021.633320

Cited by 9 publications

(27 citation statements)

References 50 publications

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“…Studies have shown neurobehavioral, pathophysiological and pathological alterations after a single traumatic insult; but despite some variability in results in repeat insult models reflecting methodological differences, the overall data demonstrates far worse longitudinal outcomes following rTBI and mmTBI. Through Hill's criterion of experiment, the findings from pre-clinical RHI studies replicating elements of observed human pathophysiological (140,141), imaging (142,143), and epidemiological studies (21) suggests a causal relationship.…”

Section: Methodsmentioning

confidence: 99%

Applying the Bradford Hill Criteria for Causation to Repetitive Head Impacts and Chronic Traumatic Encephalopathy

Nowinski¹,

Bureau²,

Buckland

et al. 2022

Front. Neurol.

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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.

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Section: Methodsmentioning

confidence: 99%

Applying the Bradford Hill Criteria for Causation to Repetitive Head Impacts and Chronic Traumatic Encephalopathy

Nowinski¹,

Bureau²,

Buckland

et al. 2022

Front. Neurol.

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show abstract

“…We have previously employed the fatigue and related symptom survey to characterise and quantify our cohorts, particularly those who express ongoing self-reported symptoms compared to those who report no ongoing symptoms (Pearce et al, 2020; Pearce et al, 2021). We found significant differences between the groups we studied, with the self-concern group having the highest scores.…”

Section: Discussionmentioning

confidence: 99%

“…Employing previously published methods in similar cohorts (Pearce et al, 2014; Pearce et al, 2021; Pearce et al, 2018), corticospinal excitability was quantified via single-pulse TMS, delivered over the contralateral primary motor cortex. Surface electromyography (sEMG) measured motor evoked potentials (MEPs) recording 500 ms sweeps (100 ms pre-trigger, 400 ms post-trigger; PowerLab 4/35, ADInstruments, Australia).…”

Section: Methodsmentioning

confidence: 99%

“…With the most influencing confounding factor on cSP duration being the preceding MEP (Škarabot et al, 2019), we employed MEP:cSP ratio to compare between groups and reduce between-participant variability (Orth & Rothwell, 2004). We have previously published MEP:cSP ratios in a cohort with persistent post-concussion symptoms (Pearce et al, 2020) and more recently in larger project on retired contact sport athletes (Pearce et al, 2021).…”

Section: Methodsmentioning

confidence: 99%

“…Our previous work on sensorimotor and neurophysiology of individuals with persistent post-concussion symptoms (Pearce et al, 2020), and chronic long-term outcomes in retired athletes (Pearce et al, 2021), demonstrated slower sensorimotor reaction time in symptomatic individuals when compared with controls. Here we present our studies of response time in two groups of retired contact sport athletes’: one with ongoing concerns about their cognitive health and the other with no ongoing concerns.…”

Section: Introductionmentioning

confidence: 98%

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Assessment of somatosensory and cognitive-motor processing time in retired athletes with a history of repeated head trauma

Pearce

Kidgell

et al. 2022

Preprint

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Measurement of the adverse outcomes of repeated head trauma in contact sport athletes is often achieved using tests where the comparator is the ‘score’ or the ‘accuracy’ obtained. While it is expected that ex-athletes would perform worse than controls, previous studies have shown inconsistent results. Here we have attempted to address these inconsistencies from a different perspective by quantifying not only accuracy, but also the time of motor responses (response time). We tested age-matched control subjects who have never experienced head trauma (n=20; 41.8 ± 14.4 years), and two cohorts of retired contact sport athletes with a history of head trauma and concussions; one with self-reported concerns (n=36; 45.4 ± 12.6 years), and another with no ongoing concerns (n=19; 43.1 ± 13.5 years). Participants performed cognitive (Cogstate) and somatosensory (Cortical Metrics) testing and both accuracy and response time were recorded. Transcranial magnetic stimulation (TMS) was undertaken to investigate corticospinal conduction and excitability. Results showed that in both test batteries there was little difference between groups when considering only accuracy scores. By contrast, response times in all but one test revealed that ex-athletes with self-reported concerns were significantly slower compared to no concern ex-athlete or control groups (p ranges 0.031 to <0.001). TMS latency showed significantly increased conduction time (p=0.008) in the group with ongoing concerns. These findings suggest that incorporating response times in cognitive and somatosensory testing is more informative than considering accuracy scores alone when assessing cognitive processing ability in retired contact sport athletes with ongoing brain health concerns.

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The Interval Between Concussions Does Not Influence Time to Asymptomatic or Return to Play: A CARE Consortium Study

Shumski,

Eagle,

Kontos

et al. 2024

Sports Med

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Chronic Neurophysiological Effects of Repeated Head Trauma in Retired Australian Male Sport Athletes

Cited by 9 publications

References 50 publications

Applying the Bradford Hill Criteria for Causation to Repetitive Head Impacts and Chronic Traumatic Encephalopathy

Applying the Bradford Hill Criteria for Causation to Repetitive Head Impacts and Chronic Traumatic Encephalopathy

Assessment of somatosensory and cognitive-motor processing time in retired athletes with a history of repeated head trauma

The Interval Between Concussions Does Not Influence Time to Asymptomatic or Return to Play: A CARE Consortium Study

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