Sports Medicine Research: In the Lab & In the Field: Could Playing Contact Sports in High School and College Increase Risk of CTE? (Sports Med Res)

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Monday, August 27, 2018

Could Playing Contact Sports in High School and College Increase Risk of CTE?

Lewy Body Pathology and Chronic Traumatic Encephalopathy Associated With Contact Sports

Adams JW, Alvarez VE, Mez J, Huber BR, Tripodis Y, Xia W, Meng G, Kubilus CA, Cormier K, Kiernan PT, Daneshvar DH, Chua AS, Svirsky S, Nicks R, Abdolmohammadi B, Evers L, Solomon TM, Cherry JD, Aytan N, Mahar I, Devine S, Auerbach S, Alosco ML, Nowinski CJ, Kowall NW, Goldstein LE, Dwyer B, Katz DI, Cantu RC, Stern RA, Au R, McKee AC, Stein TD.J Neuropathol Exp Neurol. 2018 June [Epub ahead of print]

Take Home Message: Longer participation in contact sport may increase risk of developing Lewy body diseases and chronic traumatic encephalopathy.

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Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with repetitive head impact. Clinically, CTE is often characterized by abnormal behavior (depression, more explosive) and can be difficult to distinguish from other diseases (e.g., Alzheimer’s disease, Lewy body diseases) due to the overlap in symptoms and comorbidity. However, the role of repetitive head impacts in contact sports and CTE in the development of Lewy body diseases – a leading cause of dementia –  and Parkinson’s is unknown. Therefore, to determine the association between repetitive head impacts and neuropathological diagnosis of CTE and Lewy body diseases, the authors evaluated the brains of 694 participants from 3 brain donation banks (269 from Veteran’s Affairs-Boston University-Concussion Legacy Foundation’s [UNITE group] brain bank; 261 from Boston University’s Alzheimer’s Disease Center’s brain bank; and 164 from Framingham Heart Study’s bank). To determine repetitive head impact exposure, the donor’s next of kin was interviewed; however, athletic history was not available from the Alzheimer’s Disease Center’s brain bank. Brain tissue was assessed for neuropathological conditions (Lewy body diseases, CTE, Alzheimer’s disease) by immunohistochemistry and enzyme-linked immunosorbent assay (ELISA) to measure abnormal protein deposition (alpha-synuclein, tau, amyloid-beta). Eighty-one percent of the UNITE group was diagnosed with CTE, where CTE was only diagnosed in 1% of the Framingham group and 3% of the Alzheimer’s Disease Center’s group. Alzheimer’s disease was diagnosed among 13% of the UNITE donors, 40% of the Framingham group, and 72% of the Alzheimer’s Disease Center’s group. Lewy body diseases was more common in the Alzheimer’s Disease Center’s group (44%) compared with the UNITE (20%) or Framingham (31%). Participating in a contact sport for more than 8 years was the biggest predictor of Lewy body diseases in all groups combined (6 times greater risk).

This is a notable study because it is the first to look for CTE in a large population of brains not selected solely on sport participation. The authors found that the number of years exposed to contact sports was associated with the development of Lewy body diseases and CTE. Previous studies have not used community samples and typically recruited brains from sports, primarily contact sports such as football. This prevented researchers from being able to determine if CTE was present in the general population, let alone determine if athletes were more likely to have CTE than the average person. It should be noted that these findings need to be confirmed because of several limitations: 1) missing data on repetitive head impact exposure from the Alzheimer’s Disease Center’s group, 2) a vast difference in repetitive head impact exposures and the age of the tissue between the Framingham and UNITE groups, and 3) the UNITE group is not a random sample of athletes but one that may bias the results. Despite these limitations, the authors showed that in two groups not selected based on sport participation the prevalence of CTE is low. Medical professionals should be aware of the possible risks associated with exposure to head impacts and should be educating coaches, parents and athletes on safer practices to limit head impact exposure and the risks of repetitive head impacts. Clinicians should also be able to explain the difference between some of the claims in the news and what the available evidence is able to tell us.

Questions for Discussion: Do you think athletes would be more likely to report head impacts if they knew it could lead to a long-term disease like CTE? Do you believe there would be an increased risk of CTE pathology in athletes that start contact sport in middle school or younger youth leagues?

Written by: Jane McDevitt
Reviewed by: Jeffrey Driban

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