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What is CTE?
CTE, which stands for chronic traumatic encephalopathy, is a brain disease associated with repeated traumatic brain injuries. Here is what's known about it.
Repeated blows to the head in contact sports may trigger significant brain changes years before chronic traumatic encephalopathy (CTE) becomes visible, according to new research supported by the National Institutes of Health.
The findings suggest that damage to neurons, immune system activation, and blood vessel changes in the brain can occur in athletes as young as their 20s and 30s — far earlier than scientists have previously been able to detect signs of CTE.
CTE, a progressive brain disease tied to repeated head trauma, is currently only diagnosable after death. By identifying early cellular damage, researchers say doctors may one day be able to detect and treat CTE before symptoms develop.
"This study underscores that many changes in the brain can occur after repetitive head impacts," said Dr. Walter Koroshetz, director of NIH’s National Institute of Neurological Disorders and Stroke. "These early brain changes might help diagnose and treat CTE earlier than is currently possible now."
What the study reveals about early brain damage in athletes
What we know:
The study, conducted by scientists at the Boston University CTE Center, the U.S. Department of Veterans Affairs Boston Healthcare System, and other institutions, examined postmortem brain tissue from athletes younger than 51, most of whom played football.
Key findings include:
- A 56% loss of a specific type of neuron in brain regions most affected by hard impacts, even in athletes without tau buildup.
- A strong link between years of playing contact sports and both neuron loss and immune system activation.
- Microglia — the brain’s immune cells — became more active with increased exposure to repetitive impacts.
- Blood vessel changes, including thickening and gene activity suggesting immune response and reduced oxygen in brain tissue.
Researchers also found a new communication pathway between microglia and blood vessel cells that may help explain how damage spreads before CTE fully develops.
What we don't know:
The study did not determine why some athletes develop more severe symptoms or how these early brain changes translate into long-term risks. It also remains unclear whether certain protective measures could slow or prevent the progression from early damage to CTE.
How repeated head impacts affect young athletes’ brains
The backstory:
Most research on CTE has focused on older athletes with advanced disease. This study is among the first to look at younger athletes, revealing cellular-level changes years before the disease’s hallmark tau protein tangles appear.
"What’s striking is the dramatic cellular changes, including significant, location-specific neuron loss in young athletes who had no detectable CTE," said Dr. Richard Hodes, director of NIH’s National Institute on Aging. "Understanding these early events may help us protect young athletes today as well as reduce risks for dementia in the future."
Brain scans show areas of damage linked to chronic traumatic encephalopathy (CTE), a degenerative brain condition associated with repeated head impacts in athletes. (Jeff Siner/Charlotte Observer/MCT)
The other side:
Sports leagues, including the NFL, have introduced new concussion protocols, helmet technology, and practice limitations to reduce head impacts. Still, critics argue that these measures may not be enough to prevent long-term brain injury in athletes who sustain repeated hits over years of play.
What's next:
The researchers say their findings lay the groundwork for developing early diagnostic tools and potential interventions to protect athletes before irreversible brain damage sets in.
The Source: This report is based on findings published by researchers from Boston University, the Department of Veterans Affairs, and NIH’s National Institute of Neurological Disorders and Stroke and National Institute on Aging.