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Fortington LV, Cassidy JD, Castellani RJ, Gardner AJ, McIntosh AS, Austen M, Kerr ZY, Quarrie KL. Epidemiological Principles in Claims of Causality: An Enquiry into Repetitive Head Impacts (RHI) and Chronic Traumatic Encephalopathy (CTE). Sports Med 2024:10.1007/s40279-024-02102-4. [PMID: 39277838 DOI: 10.1007/s40279-024-02102-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/05/2024] [Indexed: 09/17/2024]
Abstract
Determining whether repetitive head impacts (RHI) cause the development of chronic traumatic encephalopathy (CTE)-neuropathological change (NC) and whether pathological changes cause clinical syndromes are topics of considerable interest to the global sports medicine community. In 2022, an article was published that used the Bradford Hill criteria to evaluate the claim that RHI cause CTE. The publication garnered international media attention and has since been promoted as definitive proof that causality has been established. Our counterpoint presents an appraisal of the published article in terms of the claims made and the scientific literature used in developing those claims. We conclude that the evidence provided does not justify the causal claims. We discuss how causes are conceptualised in modern epidemiology and highlight shortcomings in the current definitions and measurement of exposures (RHI) and outcomes (CTE). We address the Bradford Hill arguments that are used as evidence in the original review and conclude that assertions of causality having been established are premature. Members of the scientific community must be cautious of making causal claims until the proposed exposures and outcomes are well defined and consistently measured, and findings from appropriately designed studies have been published. Evaluating and reflecting on the quality of research is a crucial step in providing accurate evidence-based information to the public.
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Affiliation(s)
- Lauren V Fortington
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia.
| | - J David Cassidy
- Division of Epidemiology, Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada
| | - Rudolph J Castellani
- Division of Neuropathology, Northwestern University Feinberg School of Medicine and Mesulam Center for Cognitive Neurology and Alzheimer's Disease, Chicago, IL, USA
| | - Andrew J Gardner
- Sydney School of Health Sciences, Faculty of Medicine and Health, The University of Sydney, Camperdown, NSW, Australia
| | - Andrew S McIntosh
- Monash University Accident Research Centre, Monash University, Clayton, VIC, Australia
| | - Michael Austen
- Australasian Faculty of Occupational and Environmental Medicine, Royal Australasian College of Physicians, Sydney, Australia
- Royal New Zealand College of Urgent Care, Auckland, New Zealand
- High Court of New Zealand, Auckland, New Zealand
| | - Zachary Yukio Kerr
- Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Kenneth L Quarrie
- New Zealand Rugby, 100 Molesworth Street, Wellington, New Zealand
- Sports Performance Research Institute New Zealand (SPRINZ), Auckland University of Technology, Auckland, New Zealand
- Auckland Bioengineering Institute (ABI), The University of Auckland, Auckland, Auckland, New Zealand
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Del Bigio MR, Krawitz S, Sinha N. Chronic traumatic encephalopathy-neuropathologic change in a routine neuropathology service: 7-year follow-up. J Neuropathol Exp Neurol 2023; 82:948-957. [PMID: 37846159 PMCID: PMC10588000 DOI: 10.1093/jnen/nlad079] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2023] Open
Abstract
To follow our 2016 study of chronic traumatic encephalopathy neuropathologic change (CTE-NC) in our forensic autopsy service, we prospectively screened all cases with clinical histories of multiple concussions, persistent post-head injury symptoms, or ≥3 hospital investigations for head injuries from 2016 to 2022 inclusive using hyperphosphorylated tau (p-tau) immunostaining. The cases had routine brain sampling plus 4-6 additional lateral hemisphere samples. When "pathognomonic" CTE-NC lesions were identified, additional p-tau immunostaining was done for CTE-NC staging. Of ∼1100 adult brains aged 18-65 years examined, 85 were screened, and 16 were positive for CTE-NC (2 women, 14 men, ages 35-61 years, median 47 years). Alcohol abuse was documented in 14 of 16 (8 in combination with other substances); 5 had developmental brain anomalies (2 presumed genetic, 3 from acquired perinatal insults). Widespread p-tau deposits (high CTE-NC) were found in 7 of 16. Old brain contusions were present in 9 of 16, but CTE-NC did not colocalize. Of particular interest were (1) a man with FGFR3 mutation/hypochondroplasia and life-long head banging, (2) a woman with cerebral palsy and life-long head banging, and (3) a man with bilateral peri-Sylvian polymicrogyria, alcohol abuse, and multiple head injuries. Thus, CTE-NC occurs in association with repeated head trauma outside contact sports. Substance abuse is a common determinant of risk behavior. The utility of diagnosing mild-/low-stage CTE-NC in this population remains to be determined.
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Affiliation(s)
- Marc R Del Bigio
- Department of Pathology, University of Manitoba & Shared Health Manitoba, Winnipeg, Manitoba, Canada
| | - Sherry Krawitz
- Department of Pathology, University of Manitoba & Shared Health Manitoba, Winnipeg, Manitoba, Canada
| | - Namita Sinha
- Department of Pathology, University of Manitoba & Shared Health Manitoba, Winnipeg, Manitoba, Canada
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McKee AC, Stein TD, Huber BR, Crary JF, Bieniek K, Dickson D, Alvarez VE, Cherry JD, Farrell K, Butler M, Uretsky M, Abdolmohammadi B, Alosco ML, Tripodis Y, Mez J, Daneshvar DH. Chronic traumatic encephalopathy (CTE): criteria for neuropathological diagnosis and relationship to repetitive head impacts. Acta Neuropathol 2023; 145:371-394. [PMID: 36759368 PMCID: PMC10020327 DOI: 10.1007/s00401-023-02540-w] [Citation(s) in RCA: 44] [Impact Index Per Article: 44.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 01/16/2023] [Accepted: 01/18/2023] [Indexed: 02/11/2023]
Abstract
Over the last 17 years, there has been a remarkable increase in scientific research concerning chronic traumatic encephalopathy (CTE). Since the publication of NINDS-NIBIB criteria for the neuropathological diagnosis of CTE in 2016, and diagnostic refinements in 2021, hundreds of contact sport athletes and others have been diagnosed at postmortem examination with CTE. CTE has been reported in amateur and professional athletes, including a bull rider, boxers, wrestlers, and American, Canadian, and Australian rules football, rugby union, rugby league, soccer, and ice hockey players. The pathology of CTE is unique, characterized by a pathognomonic lesion consisting of a perivascular accumulation of neuronal phosphorylated tau (p-tau) variably alongside astrocytic aggregates at the depths of the cortical sulci, and a distinctive molecular structural configuration of p-tau fibrils that is unlike the changes observed with aging, Alzheimer's disease, or any other tauopathy. Computational 3-D and finite element models predict the perivascular and sulcal location of p-tau pathology as these brain regions undergo the greatest mechanical deformation during head impact injury. Presently, CTE can be definitively diagnosed only by postmortem neuropathological examination; the corresponding clinical condition is known as traumatic encephalopathy syndrome (TES). Over 97% of CTE cases published have been reported in individuals with known exposure to repetitive head impacts (RHI), including concussions and nonconcussive impacts, most often experienced through participation in contact sports. While some suggest there is uncertainty whether a causal relationship exists between RHI and CTE, the preponderance of the evidence suggests a high likelihood of a causal relationship, a conclusion that is strengthened by the absence of any evidence for plausible alternative hypotheses. There is a robust dose-response relationship between CTE and years of American football play, a relationship that remains consistent even when rigorously accounting for selection bias. Furthermore, a recent study suggests that selection bias underestimates the observed risk. Here, we present the advances in the neuropathological diagnosis of CTE culminating with the development of the NINDS-NIBIB criteria, the multiple international studies that have used these criteria to report CTE in hundreds of contact sports players and others, and the evidence for a robust dose-response relationship between RHI and CTE.
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Affiliation(s)
- Ann C McKee
- VA Boston Healthcare System, U.S. Department of Veteran Affairs, Boston, MA, USA.
- Boston University Alzheimer's Disease Research Center and CTE Centers, Department of Neurology, Boston University School of Medicine, 150 S Huntington Ave, Boston, MA, 02130, USA.
- Department of Neurology, Boston University School of Medicine, Boston, MA, USA.
- Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, MA, USA.
- VA Bedford Healthcare System, Bedford, MA, USA.
| | - Thor D Stein
- VA Boston Healthcare System, U.S. Department of Veteran Affairs, Boston, MA, USA
- Boston University Alzheimer's Disease Research Center and CTE Centers, Department of Neurology, Boston University School of Medicine, 150 S Huntington Ave, Boston, MA, 02130, USA
- Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, MA, USA
- VA Bedford Healthcare System, Bedford, MA, USA
| | - Bertrand R Huber
- VA Boston Healthcare System, U.S. Department of Veteran Affairs, Boston, MA, USA
- Boston University Alzheimer's Disease Research Center and CTE Centers, Department of Neurology, Boston University School of Medicine, 150 S Huntington Ave, Boston, MA, 02130, USA
- Department of Neurology, Boston University School of Medicine, Boston, MA, USA
- Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, MA, USA
| | - John F Crary
- Departments of Pathology, Neuroscience, and Artificial Intelligence and Human Health, Neuropathology Brain Bank and Research Core, Ronald M. Loeb Center for Alzheimer's Disease, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Kevin Bieniek
- Department of Pathology and Laboratory Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
- Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Dennis Dickson
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA
| | - Victor E Alvarez
- VA Boston Healthcare System, U.S. Department of Veteran Affairs, Boston, MA, USA
- Boston University Alzheimer's Disease Research Center and CTE Centers, Department of Neurology, Boston University School of Medicine, 150 S Huntington Ave, Boston, MA, 02130, USA
- Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, MA, USA
- VA Bedford Healthcare System, Bedford, MA, USA
| | - Jonathan D Cherry
- VA Boston Healthcare System, U.S. Department of Veteran Affairs, Boston, MA, USA
- Boston University Alzheimer's Disease Research Center and CTE Centers, Department of Neurology, Boston University School of Medicine, 150 S Huntington Ave, Boston, MA, 02130, USA
- Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, MA, USA
| | - Kurt Farrell
- Departments of Pathology, Neuroscience, and Artificial Intelligence and Human Health, Neuropathology Brain Bank and Research Core, Ronald M. Loeb Center for Alzheimer's Disease, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Morgane Butler
- Boston University Alzheimer's Disease Research Center and CTE Centers, Department of Neurology, Boston University School of Medicine, 150 S Huntington Ave, Boston, MA, 02130, USA
| | - Madeline Uretsky
- Boston University Alzheimer's Disease Research Center and CTE Centers, Department of Neurology, Boston University School of Medicine, 150 S Huntington Ave, Boston, MA, 02130, USA
| | - Bobak Abdolmohammadi
- Boston University Alzheimer's Disease Research Center and CTE Centers, Department of Neurology, Boston University School of Medicine, 150 S Huntington Ave, Boston, MA, 02130, USA
| | - Michael L Alosco
- Boston University Alzheimer's Disease Research Center and CTE Centers, Department of Neurology, Boston University School of Medicine, 150 S Huntington Ave, Boston, MA, 02130, USA
- Department of Neurology, Boston University School of Medicine, Boston, MA, USA
| | - Yorghos Tripodis
- Boston University Alzheimer's Disease Research Center and CTE Centers, Department of Neurology, Boston University School of Medicine, 150 S Huntington Ave, Boston, MA, 02130, USA
- Department of Biostatistics, Boston University School of Public Health, Boston, MA, USA
- Department of Epidemiology, Boston University School of Public Health, Boston, MA, USA
| | - Jesse Mez
- Boston University Alzheimer's Disease Research Center and CTE Centers, Department of Neurology, Boston University School of Medicine, 150 S Huntington Ave, Boston, MA, 02130, USA
- Department of Neurology, Boston University School of Medicine, Boston, MA, USA
| | - Daniel H Daneshvar
- Boston University Alzheimer's Disease Research Center and CTE Centers, Department of Neurology, Boston University School of Medicine, 150 S Huntington Ave, Boston, MA, 02130, USA
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA, USA
- Department of Physical Medicine and Rehabilitation, Massachusetts General Hospital, Boston, MA, USA
- Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Boston, MA, USA
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Nowinski CJ, Bureau SC, Buckland ME, Curtis MA, Daneshvar DH, Faull RLM, Grinberg LT, Hill-Yardin EL, Murray HC, Pearce AJ, Suter CM, White AJ, Finkel AM, Cantu RC. Applying the Bradford Hill Criteria for Causation to Repetitive Head Impacts and Chronic Traumatic Encephalopathy. Front Neurol 2022; 13:938163. [PMID: 35937061 PMCID: PMC9355594 DOI: 10.3389/fneur.2022.938163] [Citation(s) in RCA: 46] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Accepted: 06/22/2022] [Indexed: 02/05/2023] Open
Abstract
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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Affiliation(s)
- Christopher J. Nowinski
- Concussion Legacy Foundation, Boston, MA, United States,*Correspondence: Christopher J. Nowinski
| | | | - Michael E. Buckland
- Department of Neuropathology, Royal Prince Alfred Hospital, Camperdown, NSW, Australia,School of Medical Sciences, University of Sydney, Camperdown, NSW, Australia
| | - Maurice A. Curtis
- Department of Anatomy and Medical Imaging and Centre for Brain Research, Faculty of Medical and Health Science, University of Auckland, Auckland, New Zealand
| | - Daniel H. Daneshvar
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA, United States,Department of Physical Medicine and Rehabilitation, Massachusetts General Hospital, Boston, MA, United States,Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Boston, MA, United States
| | - Richard L. M. Faull
- Department of Anatomy and Medical Imaging and Centre for Brain Research, Faculty of Medical and Health Science, University of Auckland, Auckland, New Zealand
| | - Lea T. Grinberg
- Memory and Aging Center, Department of Neurology, University of California, San Francisco, San Francisco, CA, United States,Global Brain Health Institute, University of California, San Francisco, San Francisco, CA, United States,Department of Pathology, University of Sao Paulo Medical School, São Paulo, Brazil,Department of Pathology, University of California, San Francisco, San Francisco, CA, United States
| | - Elisa L. Hill-Yardin
- School of Health and Biomedical Sciences, STEM College, RMIT University, Bundoora, VIC, Australia,Department of Anatomy & Physiology, The University of Melbourne, Parkville, VIC, Australia
| | - Helen C. Murray
- Department of Anatomy and Medical Imaging and Centre for Brain Research, Faculty of Medical and Health Science, University of Auckland, Auckland, New Zealand
| | - Alan J. Pearce
- College of Science, Health, and Engineering, La Trobe University, Melbourne, VIC, Australia
| | - Catherine M. Suter
- Department of Neuropathology, Royal Prince Alfred Hospital, Camperdown, NSW, Australia,School of Medical Sciences, University of Sydney, Camperdown, NSW, Australia
| | - Adam J. White
- Department of Sport, Health Science, and Social Work, Oxford Brookes University, Oxford, United Kingdom,Concussion Legacy Foundation UK, Cheltenham, United Kingdom
| | - Adam M. Finkel
- Department of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, MI, United States
| | - Robert C. Cantu
- Concussion Legacy Foundation, Boston, MA, United States,Department of Neurology, Boston University School of Medicine, Boston, MA, United States,Department of Neurosurgery, Emerson Hospital, Concord, MA, United States
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