Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with exposure to contact and collision sports (CCS). We hypothesized that, as duration of American football played increased, CTE neuropathological risk and severity would correspondingly increase.
We examined a convenience sample of 266 deceased American football players from two brain banks. To be eligible the VA-BU-CLF Brain Bank, donors needed a history of CCS, military service, or domestic violence, regardless of whether symptoms manifested during life. The Framingham Heart Study (FHS) Brain Bank includes participants from two generations of the FHS. All brains were processed and analyzed using identical methods with neuropathologists blinded to the participant’s CCS exposure and clinical history.
We evaluated the ability of years played to classify CTE status using regression and ROC curve analysis. Simulation analyses quantified conditions that might lead to selection bias, including age, race, dementia status, depression status, duration played, and CTE status.
Duration played was significantly associated with odds of CTE at death, with odds increasing 30% every year, and doubling every 2.6 years. Among those with CTE, duration played was also significantly associated with having severe CTE pathology and greater NFT burden. We found that even under conditions of extreme selection bias into the brain bank, the OR for the relationships between duration played and CTE outcomes had consistent magnitudes.