Sport associated dementiaBMJ 2021; 372 doi: https://doi.org/10.1136/bmj.n168 (Published 21 January 2021) Cite this as: BMJ 2021;372:n168
- William Stewart, consultant neuropathologist1
- 1Institute of Neuroscience and Psychology, University of Glasgow, and Department of Neuropathology, Queen Elizabeth University Hospital, Glasgow, UK
Recent media reports of high profile former soccer and rugby players with diagnoses of neurodegenerative disease have raised concerns about the dangers of contact sports and led to threats of litigation against sports organisations over perceived failures in duty of care.12 But are concerns that brain health is affected by participation in contact sports justified? Is there evidence supporting a link between sport and dementia, and, if so, what might be done to mitigate risk?
Traumatic brain injury is a leading risk factor for neurodegenerative disease, contributing to 3-15% of cases of dementia in the community.34 A link between traumatic brain injury in contact sport and neurodegenerative disease was first proposed almost a century ago with descriptions of punch drunk syndrome among boxers,5 and the associated pathology was later defined as dementia pugilistica.6 The concern remained largely confined to boxers throughout the 20th century. In the past 20 years, however, the pathology of dementia pugilistica—now termed chronic traumatic encephalopathy—has been increasingly recognised in athletes playing other contact sports, including soccer,7 rugby,8 and American football,9 and among others with traumatic brain injury unrelated to sport.10
Chronic traumatic encephalopathy is now widely acknowledged to be associated with a history of traumatic brain injury or exposure to repetitive head impacts.1011 Furthermore, mortality from neurodegenerative disease is higher than expected among former professional soccer players and American footballers.1213 Neurodegenerative disease risk is therefore high in former contact sports athletes, with autopsy studies on former athletes with dementia showing most had neurodegenerative pathology typical of chronic traumatic encephalopathy.789
First, do no harm
Addressing neurodegenerative disease linked to sport requires a clear understanding of the consequences of traumatic brain injury for brain health, which might be considered in three broad life periods: early life (while participating in sport and exposed to injury); mid-life (retired from sport and no longer exposed to injury); and late life (when symptoms might emerge).
To date, traumatic brain injury remains the only known risk factor for neurodegenerative disease associated with contact sports. Therefore, adopting a precautionary principle, every effort should be made to reduce exposure to head impacts during early life, and to better identify and manage traumatic brain injury in all sports.
Act to reduce harm
While prevention is a priority, retired athletes have already been exposed to the cumulative effects of traumatic brain injury and repetitive head impacts. In mid-life, therefore, the goal is to identify evidence of possible problems with brain health and act to reduce their consequences in line with current research and management of neurodegenerative disease unrelated to sport.
Knowledge regarding the mid-life onset of neurodegenerative disease has been accumulating over the past decade14 through programmes such as Prevent Dementia15 and the European Prevention of Alzheimer’s Dementia programme.16 These initiatives have informed the development of national policies (Brain Health Scotland, for example)17 and specialist brain health clinics founded to provide detailed risk profiling, detect early disease, and develop personalised prevention plans.1819 This approach provides an ideal pathway for former athletes to obtain independent specialist review and advice on how to improve brain health, which might reduce the long term consequences of previous traumatic brain injury.
Recognise late consequences
Consensus criteria for diagnosis of chronic traumatic encephalopathy are yet to be established, but the range of neurodegenerative diagnoses in former athletes is broad and not confined to diseases that are clinically similar to chronic traumatic encephalopathy.1213 Furthermore, although autopsy shows the pathology of chronic traumatic encephalopathy in most former athletes with dementia, it is not usually the primary cause of their dementia.7 Thus, while efforts to recognise chronic traumatic encephalopathy better are welcome, other neurodegenerative diagnoses associated with contact sport participation, including Alzheimer’s disease and motor neuron disease, must not be overlooked in former athletes.
The goals in later life are to recognise that sport may be implicated in an individual’s risk profile, to record all cases of neurodegenerative disease in former athletes for surveillance purposes, and to engage patients and their families in research towards understanding the influence of sport on lifelong brain health, including autopsy studies. Clinical management should always be guided by best practice protocols for whichever diagnosis is established.
Current evidence supports an association between elite level participation in contact sports and increased risk of neurodegenerative disease, which, on balance of probabilities, is a consequence of exposure to repeated head impacts. In the coming years, whether sports organisations acted appropriately to protect athletes’ brain health will be tested in the courts. In the meantime, the question for them to consider in 2021 is whether current policies are good enough to reduce risk of harm for today’s athletes.
Competing interests: The BMJ has judged that there are no disqualifying financial ties to commercial companies. The author declares the following other interests: funding from the Professional Footballers Association and the Football Association for research into football’s influence on lifelong health and dementia risk; member of the Football Association’s head injury and concussion expert panel and FIFA independent football concussion advisory group; research funding from the National Institute of Neurological Disorders and Stroke.
Provenance and peer review: Commissioned; not externally peer reviewed.