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Iverson GL, Castellani RJ, Cassidy JD, Schneider GM, Schneider KJ, Echemendia RJ, Bailes JE, Hayden KA, Koerte IK, Manley GT, McNamee M, Patricios JS, Tator CH, Cantu RC, Dvorak J. Examining later-in-life health risks associated with sport-related concussion and repetitive head impacts: a systematic review of case-control and cohort studies. Br J Sports Med 2023; 57:810-821. [PMID: 37316187 DOI: 10.1136/bjsports-2023-106890] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/26/2023] [Indexed: 06/16/2023]
Abstract
OBJECTIVE Concern exists about possible problems with later-in-life brain health, such as cognitive impairment, mental health problems and neurological diseases, in former athletes. We examined the future risk for adverse health effects associated with sport-related concussion, or exposure to repetitive head impacts, in former athletes. DESIGN Systematic review. DATA SOURCES Search of MEDLINE, Embase, Cochrane, CINAHL Plus and SPORTDiscus in October 2019 and updated in March 2022. ELIGIBILITY CRITERIA Studies measuring future risk (cohort studies) or approximating that risk (case-control studies). RESULTS Ten studies of former amateur athletes and 18 studies of former professional athletes were included. No postmortem neuropathology studies or neuroimaging studies met criteria for inclusion. Depression was examined in five studies in former amateur athletes, none identifying an increased risk. Nine studies examined suicidality or suicide as a manner of death, and none found an association with increased risk. Some studies comparing professional athletes with the general population reported associations between sports participation and dementia or amyotrophic lateral sclerosis (ALS) as a cause of death. Most did not control for potential confounding factors (eg, genetic, demographic, health-related or environmental), were ecological in design and had high risk of bias. CONCLUSION Evidence does not support an increased risk of mental health or neurological diseases in former amateur athletes with exposure to repetitive head impacts. Some studies in former professional athletes suggest an increased risk of neurological disorders such as ALS and dementia; these findings need to be confirmed in higher quality studies with better control of confounding factors. PROSPERO REGISTRATION NUMBER CRD42022159486.
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Affiliation(s)
- Grant L Iverson
- Sports Concussion Program, MassGeneral Hospital for Children, Boston, Massachusetts, USA
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, Massachusetts, USA
- Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Charlestown, Massachusetts, USA
- Department of Physical Medicine and Rehabilitation, Schoen Adams Research Institute at Spaulding Rehabilitation, Charlestown, Massachusetts, USA
- Home Base, A Red Sox Foundation and Massachusetts General Hospital Program, Massachusetts General Hospital, Charlestown, Massachusetts, USA
| | - Rudolph J Castellani
- Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - J David Cassidy
- Division of Epidemiology, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
| | - Geoff M Schneider
- Department of Radiology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Kathryn J Schneider
- Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Ruben J Echemendia
- Department of Psychology, University of Missouri-Kansas City, Kansas City, Missouri, USA
- University Orthopedic Centre, Concussion Care Clinic, State College, Pennsylvania, USA
| | - Julian E Bailes
- Department of Neurosurgery, NorthShore University HealthSystem, Evanston, Illinois, USA
- Department of Neurosurgery, University of Chicago Pritzker School of Medicine, Chicago, Illinois, USA
| | - K Alix Hayden
- Libraries and Cultural Resources, University of Calgary, Calgary, Alberta, Canada
| | - Inga K Koerte
- cBRAIN, Department of Child and Adolescent Psychiatry, Psychosomatic, and Psychotherapy, University Hospital, Ludwig-Maximilians-Universität, Munich, Germany
- Department of Psychiatry, Psychiatry Neuroimaging Laboratory, Brigham and Women's Hospital, Mass General Brigham, Boston, Massachusetts, USA
- Department of Psychiatry, Massachusetts General Hospital, Boston, MA, USA
| | - Geoffrey T Manley
- Department of Neurosurgery, University of California San Francisco, San Francisco, California, USA
| | - Michael McNamee
- Department of Movement Sciences, KU Leuven, Leuven, Belgium
- School of Sport and Exercise Sciences, Swansea University, Swansea, UK
| | - Jon S Patricios
- Wits Sport and Health (WiSH), School of Clinical Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Charles H Tator
- Department of Surgery and Division of Neurosurgery, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
- Canadian Concussion Centre, Toronto Western Hospital, Toronto, Ontario, Canada
| | - Robert C Cantu
- Department of Neurology, Boston University School of Medicine, Boston, Massachusetts, USA
- Robert C. Cantu Concussion Center, Emerson Hospital, Concord, Massachusetts, USA
| | - Jiri Dvorak
- Schulthess Clinic Zurich, Zurich, Switzerland
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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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Buckland ME, Affleck AJ, Pearce AJ, Suter CM. Chronic Traumatic Encephalopathy as a Preventable Environmental Disease. Front Neurol 2022; 13:880905. [PMID: 35769361 PMCID: PMC9234108 DOI: 10.3389/fneur.2022.880905] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 05/06/2022] [Indexed: 11/29/2022] Open
Abstract
In this Perspective we explore the evolution of our understanding of chronic traumatic encephalopathy (CTE) and its relationship with repetitive head injury. As with many neurodegenerative conditions, there is an imperfect correspondence between neuropathology and clinical phenotype, but unlike other neurodegenerative diseases, CTE has a discrete and easily modifiable risk factor: exposure to repetitive head injury. Consequently, evaluation of the evidence regarding exposure to repetitive head injury and CTE risk should be undertaken using public or occupational health frameworks of medical knowledge. The current debate over the existence of CTE as a disease of concern is fuelled in part by immediate medico-legal considerations, and the involvement of high-profile athletes, with inevitable media interest. Moving beyond this debate has significant potential to address and reduce disease impact in the near future, and provide novel insights into mechanisms underlying abnormal protein accumulation in CTE and other neurodegenerative diseases.
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Affiliation(s)
- Michael E. Buckland
- Department of Neuropathology, Royal Prince Alfred Hospital, Camperdown, NSW, Australia
- School of Medical Sciences, University of Sydney, Camperdown, NSW, Australia
- *Correspondence: Michael E. Buckland
| | - Andrew J. Affleck
- Department of Neuropathology, Royal Prince Alfred Hospital, Camperdown, NSW, Australia
| | - Alan J. Pearce
- College of Science, Health and Engineering, La Trobe University, Bundoora, 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
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Zuckerman SL, Yengo-Kahn AM, Brett BL, Kuhn AW, Wolfson DI, Kerr ZY. Benefits of team sport participation versus concerns of chronic traumatic encephalopathy: prioritizing the health of our youth. Concussion 2020; 5:CNC75. [PMID: 32509327 PMCID: PMC7270841 DOI: 10.2217/cnc-2020-0006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Affiliation(s)
- Scott L Zuckerman
- Vanderbilt Sports Concussion Center, Vanderbilt University Medical Center, Nashville, TN 37232, USA.,Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Aaron M Yengo-Kahn
- Vanderbilt Sports Concussion Center, Vanderbilt University Medical Center, Nashville, TN 37232, USA.,Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Benjamin L Brett
- Department of Neurology, Medical College of Wisconsin, Milwaukee, WI 53226, USA.,Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Andrew W Kuhn
- Vanderbilt Sports Concussion Center, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Daniel I Wolfson
- Vanderbilt Sports Concussion Center, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Zachary Y Kerr
- Department of Exercise & Sport Science, University of North Carolina at Chapel Hill, Chapel Hill, NC 27154, USA.,Matthew Gfeller Sport-Related Traumatic Brain Injury Research Center, University of North Carolina, Chapel Hill, NC 27154, USA.,Injury Prevention Research Center, University of North Carolina, Chapel Hill, NC, USA
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