The repeated impacts of the head cause early loss of neurons and inflammation in young athletes

Wednesday September 17, 2025

The study funded by the NIH reveals brain changes long before chronic traumatic encephalopathy (CTE) is developing.

Research supported by the National Institutes of Health (NIH) shows that the repeated impacts of the head of contact sports can cause early and lasting changes in the brain of young to medium athletes. The results show that these changes can arise for years before chronic traumatic encephalopathy (CTE) develops its characteristic characteristics characteristics, which can now be detected by examining brain tissue after death.

“This study stresses that many changes in the brain can occur after repetitive head impacts,” said Walter Koroshetz, MD, director of the National Institute of Neurological Disorders and Stroke (NIDS) of the NIH. “These first brain changes could help diagnose and treat CTE earlier than what is currently possible now.”

Scientists from the Boston University CTE Center, from the American department of Boston Healthcare System veterans and collaboration institutions have analyzed the post-mortal cerebral tissues under 51. Most of them had played American football. The team examined the brain tissue of these athletes, using advanced tools that follow the activity of genes and images in individual cells. Many of these tools have been launched by NIH Brain research by making innovative neurotechnologies progress® Initiative or The Brain Initiative®. The researchers have identified many additional changes in the brain beyond the usual molecular signature known to scientists: accumulation of a protein called tau in nerve cells next to small blood vessels deeply in the folds of the brain.

For example, researchers found a striking loss of 56% of a specific type of neurons in this particular brain zone, which takes hard blows during the impacts and also where the Tau protein accumulates. This loss was obvious even among athletes who had no accumulation of tau. He also followed with the number of years of exposure to the repetitive impacts of the head. The results therefore suggest that neural damage can occur much earlier than what is visible by the Marker of the CTE is currently known Tau. The team also observed that the immune cells of the brain, called microglies, were increasingly activated in proportion to the number of years that athletes had practiced contact sports.

The study also revealed significant molecular changes in blood vessels of the brain. These changes included gene models that could point out an immune activity, a possible reaction to lower oxygen levels in the nearby brain tissue, and thickening and growth of small blood vessels. With these results, the researchers identified a newly described communication route between microglia and blood vessels cells. The authors suggest that this diaphony can help explain how early cellular problems have prepared the ground for the progression of the disease long before the CTE became visible.

The study is one of the first to focus on younger athletes, paying the attention of the advanced CTE in the elderly to the first cellular signatures of damage.

“What is striking are the spectacular cellular changes, including a significant and specific loss of neurons in the location in young athletes who did not have a detectable CTE,” said Richard Hodes, MD, director of the National Institute on Aging (NIA). “Understanding these first events can help us protect young athletes today and reduce the risks for dementia in the future.”

By revealing the first signs of cell warning, this work lays the basis of new ways of detecting the brain effects of repetitive head trauma and potentially lead to interventions that could prevent the devastating neurodegeneration of the CTE.

This research was supported by Ninds and NIA through subsidies F31NS132407, U19AG068753, RF1G057902, R01AG062348, R01AG090553, U54NS115266 and P30AG072978.

About the National Institute of Neurological Disorders and Cerebral Vascular Accidents (Ninds): Ninds is the main funder for the brain research and the nervous system. Ninds’ mission is to seek fundamental knowledge about the brain and the nervous system and use this knowledge to reduce the burden of neurological diseases. https://www.ninds.nih.gov/

About the National Institute of Aging (NIA): Nia seeks to understand the nature of aging and diseases associated with the old old, in order to extend the healthy and active years of life. https://www.nia.nih.gov

On the National Institutes of Health (NIH): The NIH, the country’s medical research agency, includes 27 institutes and centers and is a component of the American department of health and social services. NIH is the main federal agency that leads and supports basic, clinical and translational medical research, and studies the causes, treatments and remedies for common and rare diseases. For more information on the NIH and its programs, visit www.nih.gov.

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Reference

Butler MLMD, Perviz N, Breen K. et al. Repeated head trauma causes loss of neurons and inflammation in young athletes. Nature (2025). DOI: 10.1038 / S41586-025-09534-6