It’s been long known that people who have traumatic brain injuries are at an increased risk for a progressive brain disorder called chronic traumatic encephalopathy (CTE). They also are at increased risk for parkinsonism, like the movement problems of Parkinson’s disease. But what is the risk of exposure to years of repetitive, milder head impacts such as those from contact sports?
New research suggests that amateur and professional athletes who play contact sports are also at greater risk of developing dementia, parkinsonism and the presence of Lewy bodies (LB) in the brain, called LB disease. LB disease causes several disorders, including Lewy body dementia and Parkinson’s disease.
Researchers at Boston University’s Alzheimer’s and CTE Center studied donated brains from three different research cohorts - 269 athletes who played amateur or professional contact sports, 261 study participants at the BU Alzheimer’s Research Center, and 164 participants from an aging study. The study team looked at the brains for progressive neurological diseases, clinical records for related symptoms during life, and at the distribution of the brain diseases through different regions of the brain.
As expected the cohort from the aging study had the most subjects free of any significant brain disease. Similarly, the Alzheimer’s Center cohort had the largest percentage of Alzheimer’s disease (AD) diagnoses at autopsy. Dementia during life was associated with frequency of LB disease, the severity of CTE pathology, and the presence of AD pathology. Also, as expected all cases of CTE were in individuals who had a history of playing contact sports, regardless of which cohort they were from. Over 80% of cohort of athletes had CTE and 20% had LB disease.
But the study included some very interesting findings. Individuals who played contact sports longer (8 years or more) were more likely to have dementia, parkinsonism and LB disease in the neocortical (thinking) areas of the brain, even if they didn’t have CTE. Individuals with CTE+LB also died at younger ages than those with other pathologies.
CTE pathology was associated with the presence of dementia, but not symptoms of parkinsonism. The authors speculate that parkinsonism symptoms may be driven more by co-existing LB disease in CTE, rather than by CTE itself.
There were some limitations to the study. The brains from the contact-sports athletes were donated by people with particular interest in the chronic traumatic encephalopathy study, rather than a random sample of contact-sports athletes. And the study is retrospective, meaning a study of medical records and autopsy results, compared to studying individuals’ symptoms during life and comparing those clinical symptoms to autopsy results.) This means while there was an association found in this study, drawing conclusions about cause and effect is less certain than associations found in a prospective study.
The bottom line is that there is some evidence suggesting a relationship between playing contact sports and the presence of neocortical Lewy bodies, which are also found in people with Lewy body dementia. More work is needed to better understand what causes multiple disease processes in persons with CTE, and to learn if the same results would be found in a population of athletes at large and in others with non-sports related mild head impacts.