Repeated Head Impacts Cause Early Neuron Loss, Inflammation in Young Athletes
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New NIH-funded research shows repeated head impacts from contact sports can cause early and lasting changes in the brains of young- to middle-aged athletes. The findings show these changes may occur years before chronic traumatic encephalopathy (CTE) develops its hallmark disease features.
The research team analyzed postmortem brain tissue from athletes under age 51. Most of them had played American football. The team examined brain tissue from these athletes, using cutting-edge tools that track gene activity and images in individual cells. The researchers identified additional changes in brains beyond the usual molecular signature known to scientists: buildup of a protein called tau in nerve cells next to small blood vessels deep in the brain’s folds.
For example, the researchers found a striking 56% loss of a specific type of neuron in that same brain area, which takes hard hits during impacts and also accumulates tau. This neuron loss was evident even in athletes who had no tau buildup. It also aligned with the number of years of exposure to repetitive head impacts. Thus, neuronal damage may occur much earlier than is visible. The team also observed that the brain’s immune cells, called microglia, became increasingly activated in proportion to the number of years the athletes had played contact sports.
The brain’s blood vessels also experience significant molecular changes. Some gene patterns could signal immune activity, like a reaction to lower oxygen levels in nearby brain tissue and thickening and growth of small blood vessels. From these findings, the researchers identified a new communication pathway between microglia and blood vessel cells. This crosstalk may help explain how early cellular problems set the stage for disease progression long before CTE becomes visible.
The study is one of the first to focus on younger athletes, shifting attention from advanced CTE in older people to the earliest cellular signatures of damage.
By revealing the earliest cellular warning signs, this work lays the foundation for new ways to detect brain effects of repetitive head injuries and potentially lead to interventions that could prevent devastating CTE neurodegeneration.