Relationship Between Level of American Football Playing and Diagnosis of Chronic Traumatic Encephalopathy in a Selection Bias Analysis

Abstract

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with exposure to repetitive head impacts (RHI) such as those from American football. Our understanding of this association is based on research in autopsied brains since CTE can only be diagnosed postmortem. Such studies are susceptible to selection bias, which needs to be accounted for to ensure a generalizable estimate of the association between RHI and CTE. We evaluated the relationship between level of American football play and CTE diagnosis after adjusting for selection bias. The sample included 290 deceased male former American football players who donated their brain to the Veterans Affairs-Boston University-Concussion Legacy Foundation Brain Bank (VA-BU-CLF) between 2008 and 2019. After adjusting for selection bias, college and professional football players have 2.38 (95% simulation interval (SI): 1.16,5.94) and 2.47 (95% SI: 1.46,4.79) times the risk of being diagnosed with CTE relative to high school players, respectively, which are larger than estimates with no selection bias adjustment. Since CTE is currently diagnosed only post-mortem, we additionally provide plausible scenarios for the risk ratios of these populations where we consider the outcome affecting former players during their lifetime. In conclusion, this study provides further evidence to support a dose-response relationship between football play and CTE.

Decreased myelin proteins in brain donors exposed to football-related repetitive head impacts

“…However, such selection does not negate valid RHI-CTE estimates. 14 , 110 Additionally, immunoassays for MAG and PLP were done on the white matter underlying the frontal cortex as this region is commonly affected by exposure to RHI and is the initial location of tau pathology in CTE. Examination of other regions will inform specificity.…”

Management of Neuropsychiatric Symptoms for Chronic Traumatic Encephalopathy

“…Adopting a multidisciplinary approach while treating patients with CTE is important. Sports medicine doctors and other physicians/licensed health professionals caring for athletes participating in contact sports as well as other people at risk for repeat head injury should begin thinking about ways to limit head trauma and minimize the risk for CTE long before the onset of the disease [3,[33][34][35][64][65][66][67]103]. In patients who go on to develop the disease, a variety of health care professionals may be helpful in managing the diverse symptoms and coordinating the supportive care needed by each individual patient.…”

“…Players and coaches should be counseled on the importance of following these guidelines [33,34]. Although repeat head injuries are the primary risk factor for CTE, other risk factors such as genetics, comorbidities, lifestyle, and psychosocial factors may also modulate a person's risk of disease development [3,35,[64][65][66][67]. The APOEε4 allele may be associated with worsened CTE pathology on autopsy and is suspected to worsen outcomes and recovery after TBI [35,68].…”

Dementia and Alzheimer’s disease in former contact sports participants: population-based cohort study, systematic review, and meta-analysis

“…In partial support of the finding of lower dementia rates in former high school football athletes, at autopsy, former professionals and college players had a markedly higher prevalence of chronic traumatic encephalopathy, a neurodegenerative disorder. 11…”

“…9 These observations raise concerns that lower intensity repetitive head impact, characteristic of participation in contact sports, may have implications for the occurrence of dementia. 10 Although autopsy investigations reveal evidence of chronic traumatic encephalopathy, a neurodegenerative disease, among select samples of former athletes from American football, 11 soccer, 12 and boxing, 13 whether participation in these sports is associated with a later risk of dementia is uncertain.…”