Of 202 sampled deceased former football players, CTE was neuropathologically diagnosed in 177 players (87%).  Of the 202, two participants played football only during middle school, and zero of these two developed CTE. 3 of 14 high school players (21%), 48 of 53 college (91%), 9 of 14 semiprofessional (64%),  7 of 8 Canadian Football League (88%), and 110 of 111 National Football League (99%) players were among the 177/202 diagnosed with CTE.

Michigan State University

Players of American football may be at increased risk of long-term neurological conditions, particularly chronic traumatic encephalopathy (CTE).

Chronic Traumatic Encephalopathy (CTE) and American Football

Mez J, Daneshvar DH, Abdolmohammadi B, Chua AS, Alosco ML, Kiernan PT, Evers L, Marshall L, Martin BM, Palmisano JN, Nowinski CJ, Mahar I, Cherry JD, Alvarez VE, Dwyer B, Huber BR, Stein TD, Goldstein LE, Katz DI, Cantu RC, Au R, Kowall NW, Stern RA, McClean MD, Weuve J, Tripodis Y, McKee AC. Duration of American Football Play and Chronic Traumatic Encephalopathy. Ann Neurol. 2020 Jan;87(1):116-131. doi: 10.1002/ana.25611. Epub 2019 Nov 23. PMID: 31589352; PMCID: PMC6973077.

Duration of American Football Play and Chronic Traumatic Encephalopathy

Of 27 diagnosed cases of physically "mild" CTE, 26 (96%) had behavioral and/or mood symptoms, 23 (85%) had cognitive symptoms, and 9 (33%) had signs of dementia. Three of these 27 cases had only ever played football in high school.

Mild CTE in American Football Players

Among 84 participants with severe CTE pathology, 75 (89%) had behavioral or mood symptoms or both, 80 (95%) had cognitive symptoms, and 71 (85%) had signs of dementia.

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