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
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.


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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