Repeated Head Trauma Causes Brain Damage in Athletes Before CTE Onset
Key Clinical Summary
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Single nucleus RNA sequencing of brain tissue from 28 men (ages 25–51) showed that repetitive head impacts in contact sports caused neuron loss, inflammation, and vascular injury, even without chronic traumatic encephalopathy (CTE).
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Athletes exposed to repeated head trauma had 56% fewer neurons than unexposed controls; injury localized to cortical sulcal depths, regions of highest mechanical stress.
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Repetitive head impact alone can cause early neurodegeneration; detection and preventive strategies are needed to protect at-risk athletes before CTE onset.
Even before the onset of chronic traumatic encephalopathy (CTE), contact sport athletes with exposure to repeated head trauma showed neuron loss, inflammation, and vascular damage in the brain, according to study results published in Nature.
“These results have the potential to significantly change how we view contact sports. They suggest that exposure to repetitive head impact can kill brain cells and cause long-term brain damage, independent of CTE,” said corresponding author Jonathan Cherry, PhD, of the Boston University Alzheimer’s Disease and CTE Centers at the Boston University Chobanian and Avedisian School of Medicine, Boston, Massachusetts, in a news release.
For the study, researchers performed single nucleus RNA sequencing on frozen brain tissue from 28 men aged 25 through 51 years. Among them were 8 men who did not play contact sports who served as controls, 8 men who played American football and 1 who played soccer without a diagnosis of CTE, and 11 contact sport athletes diagnosed with low-stage CTE.
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According to the findings, men with low-stage CTE showed significant inflammatory and vascular changes in the brain, as expected. However, men exposed to repetitive head impact through participation in contact sports showed levels of vascular injury and inflammation similar to the men with CTE.
In particular, men exposed to repetitive head impacts had an average 56% fewer neurons than age-matched unexposed controls. The neuron loss occurred at the cortical sulcal depths, the regions of the brain that receive the greatest mechanical force during head impact and where CTE initially develops, the research team explained. The neuron loss was seen in all athletes regardless of CTE status and was associated with the number of years of playing football or, in the case of soccer, the total years of repetitive head impact exposure.
Researchers validated the findings in larger sample sets and through comparisons with other published studies.
“These findings suggest that repetitive head impacts cause brain injury much earlier than we previously thought,” said Dr Cherry. “The risk for CTE is directly related to repetitive head impact exposure in contact sports. These results highlight that even athletes without CTE can have substantial brain injury. Understanding how these changes occur, and how to detect them during life, will help the development of better prevention strategies and treatments to protect young athletes.”
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