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“Nearly all of the former NFL players in this study had CTE pathology, and this pathology was frequently severe,” wrote senior author Ann McKee, M.D., of the Boston University (BU) CTE Center and colleagues. “These findings suggest that CTE may be related to prior participation in football and that a high level of play may be related to substantial disease burden.”
McKee and colleagues evaluated samples that were donated to a brain bank established in collaboration between the BU School of Medicine, the Boston and Bedford Veterans Administration Systems, and Concussion Legacy Foundation. A neuropathological diagnosis was made using criteria for CTE defined by an expert panel organized by the National Institute of Neurological Disorders and Stroke and National Institute of Biomedical Imaging and Bioengineering in 2015. Retrospective clinical evaluations were performed using online surveys and structured and semi-structured postmortem telephone interviews between researchers and next of kin.
CTE was identified in 177 of 202 samples, including 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%).
The severity of CTE correlated with the highest level of play, with all three former high school players having mild CTE pathology whereas 56% of college players, 56% of semiprofessional players, and 86% of professional players having severe pathology. Based on retrospective clinical evaluations, 33% of players with mild CTE had signs of dementia, compared with 85% of players with severe CTE. Players with severe CTE also had a higher occurrence of a comorbid neurological disorder such as Alzheimer’s, Lewy body disease, and frontotemporal degeneration.
Unlike the dementia differences, behavioral, mood, and/or cognitive symptoms were extremely common in players with CTE regardless of severity. Also, over 40% of the former players first sought clinical help for mood or behavioral problems. “Behavior or mood symptoms may be the initial presentation for a subset of individuals with CTE, or alternatively, CTE pathology may lower the threshold for psychiatric manifestations in susceptible individuals,” the authors wrote.
McKee and colleagues cautioned that the high frequency of CTE in this study could be exaggerated, as the brain bank is oversampled with professional football players and increasing public awareness of CTE may have motivated players with symptoms of brain injury to donate to the brain bank.
For related information, see the Journal of Neuropsychiatry and Clinical Neurosciences articles “Cognitive Reserve as a Modifier of Clinical Expression in Chronic Traumatic Encephalopathy: A Preliminary Examination” and “Suicide and Chronic Traumatic Encephalopathy.”
(Image: iStock/fredrocko)