Summary: A new JAMA study examined the brains of 202 former American football players who were donated for research and found a high frequency of chronic traumatic encephalopathy (CTE). The research team evaluated brain tissue in the laboratory and collected detailed histories from next of kin about head injuries, football participation and related factors. Of the 202 brains analyzed, 177 (87%) met neuropathological criteria for CTE. Among 111 former National Football League (NFL) players, 110 were diagnosed with CTE. The authors emphasize that these results come from a brain donation program and may overrepresent symptomatic players or families motivated by public awareness of head injury risks.
Source: JAMA Network.
Key findings
A study led by Ann C. McKee, M.D., of the Boston University CTE Center and VA Boston Healthcare System analyzed 202 donated brains from former football players to identify neuropathological evidence of CTE and to compare pathological severity with reported clinical symptoms. The research combined blinded neuropathological examinations with retrospective clinical information obtained from interviews with next of kin and questionnaires about athletic and military history.
Of the 202 players (median age at death 66), 177 (87%) had neuropathological evidence of CTE. Rates of diagnosed CTE by highest level of play were: 3 of 14 high school players (21%), 48 of 53 college players (91%), 9 of 14 semiprofessional players (64%), 7 of 8 Canadian Football League players (88%), and 110 of 111 NFL players (99%). On average, players with CTE had about 15 years of football participation.
Neuropathological severity varied with level of play. All three high school-only players with CTE had mild pathology. In contrast, the majority of former college (56%), semiprofessional (56%), and professional players (86%) showed severe CTE pathology. Clinical signs correlated with pathological stage: among 27 participants with mild CTE, nearly all (96%) had behavioral or mood symptoms, 85% had cognitive symptoms, and 33% had evidence of dementia. Among 84 participants with severe CTE, 89% had behavioral or mood symptoms, 95% had cognitive symptoms, and 85% showed signs of dementia.
The authors conclude that, in this convenience sample of donated brains, a large proportion of former football players had neuropathological evidence of CTE, which suggests an association between prior participation in football and CTE pathology. They note important factors that may influence risk and disease severity, such as age at first exposure to football, total years played, player position, and cumulative head impacts.
The investigators stress several limitations. The sample is not representative of all football players because it comprises brains donated to a research program. Public awareness of the potential link between repetitive head trauma and CTE likely influenced donation decisions, meaning families of players with symptoms or suspected brain injury may have been more likely to participate. Because of this selection bias, the study does not provide an estimate of how common CTE is among all former football players, and its high CTE frequency should be interpreted with caution.
Source: Ann C. McKee, JAMA Network.
Original research: Clinicopathological Evaluation of Chronic Traumatic Encephalopathy in Players of American Football, published online July 25, 2017, in JAMA. The study presents neuropathological diagnoses and clinical histories from a case series of donated brains and explores the relationship between level and duration of football play and CTE pathology.
Authors (selected): Jesse Mez, MD, MS; Daniel H. Daneshvar, MD, PhD; Patrick T. Kiernan, BA; Bobak Abdolmohammadi, BA; Victor E. Alvarez, MD; Bertrand R. Huber, MD, PhD; Michael L. Alosco, PhD; Todd M. Solomon, PhD; Christopher J. Nowinski, PhD; Lisa McHale, EdS; Kerry A. Cormier, BA; and Ann C. McKee, MD, among others.
Abstract (summary)
Importance: Participation in American football may increase long-term risk for neurological conditions, notably chronic traumatic encephalopathy (CTE).
Objective: To determine neuropathological and clinical features of deceased football players with CTE.
Design, Setting, and Participants: Case series of 202 football players whose brains were donated for research. Neuropathological evaluations were performed and retrospective clinical assessments with informants were conducted in a blinded fashion. Online questionnaires gathered athletic and military histories.
Exposures: Participation in American football at any level.
Main outcomes and measures: Neuropathological diagnoses of neurodegenerative disease, including CTE, based on established criteria; CTE severity staged I–IV (or grouped as mild [I–II] and severe [III–IV]); and informant-reported clinical presentation, including behavior, mood, cognition and dementia for players who died in 2014 or later.
Results: Among 202 deceased former football players (median age at death 66 years), 177 (87%) had neuropathological evidence of CTE. Median age at death for those with CTE was 67 years; mean years of football participation was about 15. Rates by highest level of play included 21% for high school-only players, 91% for college players, 64% for semiprofessional players, 88% for Canadian Football League players, and 99% for NFL players. Severe pathology was more common at higher levels of play and correlated with higher rates of cognitive impairment and dementia.
Conclusions and relevance: In this convenience sample of donated brains from former football players, a high proportion showed neuropathological evidence of CTE, suggesting a relationship between participation in football and CTE. Due to selection bias inherent in brain donation samples, these findings do not estimate overall CTE prevalence in all players.
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