Chronic traumatic encephalopathy (CTE) is a degenerative brain disorder associated with repetitive head impacts in contact sports. Studies suggest that 91.7% of deceased NFL players and approximately 40% of young players who died before age 30 had CTE. The disease is strongly linked to years played and cumulative exposure, but diagnosis can only be confirmed post-mortem.
CTE has also been frequently identified in Black athletes, who, in several studies, showed higher rates of cardiometabolic conditions such as hypertension, diabetes, and cardiovascular disease, which are all factors that independently affect cognitive health.
In a recent NIH-funded study, researchers found that severe CTE is associated with dementia.
What the Study Found
The study, published in Alzheimer’s & Dementia, was led by scientists at Boston University CTE Center and the U.S. Department of Veterans Affairs Boston Healthcare System. The researchers analyzed 614 donated brains from people with known exposure to repetitive head impacts. None of the donors had Alzheimer’s disease, Lewy body disease, or frontotemporal lobar degeneration—the three most common forms of dementia.
“By examining hundreds of brains and ruling out other common neurodegenerative diseases, the team could look at CTE alone and link it to symptoms reported during life,” said Dr. Amy Bany Adams, acting director of the NIH’s National Institute of Neurological Disorders and Stroke (NINDS).
The researchers discovered that people with stage IV CTE were 4.5 times more likely to have had dementia during life than donors without CTE. Stage III was also associated with a higher dementia risk. However, stages I-II were not found to be linked to dementia risk, cognitive impairment, or functional decline. Psychological symptoms were not observed at any stage of CTE.
These findings are substantial for furthering dementia research. “Understanding which brain changes drive cognitive decline is essential,” said Richard Hodes, director of NIH’s National Institute on Aging (NIA). “This study shows that only severe CTE has a clear link to dementia, which provides an important distinction for researchers, healthcare providers, and families.”
The study also revealed that mood or behavioral changes commonly associated with CTE may instead arise from other brain effects of repetitive head impacts or from unrelated medical or environmental factors.
The findings are part of a larger body of research indicating that young athletes who experience repetitive head impacts may elicit earlier cellular changes—such as blood vessel alterations, immune activation, and loss of certain brain cells—well before tau accumulation in the brain becomes apparent. However, researchers are still unsure whether these early brain changes cause any cognitive symptoms or lead to CTE later in life.
Why Severity Matters Clinically
One important implication of this study is the distinction between exposure to repetitive head impacts and the development of neurodegenerative disease. Historically, it’s been assumed that any presence of CTE carries dementia risk. This latest study challenges that assumption.
Only advanced stages (III-IV) of CTE were associated with cognitive impairment, while early-stage disease showed no relationship with dementia or functional decline.
For providers counseling active or retired athletes, this supports discussing risk along a spectrum rather than presenting CTE as an inevitable outcome of participation.
Differentiating CTE From Other Dementias
CTE symptoms overlap significantly with more common neurologic and psychiatric conditions. Memory complaints, irritability, depression, and executive dysfunction may signal CTE, but these features are nonspecific.
Many exposed athletes ultimately meet the criteria for other diagnoses, such as Alzheimer’s disease, vascular cognitive impairment, sleep disorder, or substance-related changes.
For practicing clinicians, exposure history should inform—not replace—a standard dementia evaluation. Treatable conditions, such as depression, sleep apnea, or medication side effects, may not account for symptoms often attributed to CTE.
How This Research Applies to Black Patients
Black athletes are overrepresented in certain collision sports and positions involving repetitive head impacts, often accumulating longer exposure over time.
Higher rates of hypertension, diabetes, and cardiovascular disease may contribute to various dementia disorders rather than CTE alone.
Behavioral changes may be attributed to psychosocial factors before neurologic evaluation, thereby delaying diagnosis. A structured assessment is essential regardless of exposure history.
Management should emphasize modifiable risk factors, including vascular health, sleep, and mental health, which may influence cognitive outcomes as much as prior sports participation.
Screening and Monitoring Former Athletes
Evaluation of former athletes should include exposure history (years played, position, age at first exposure) and functional decline, which is often more significant than isolated memory complaints. Personality changes, progressive executive dysfunction, or midlife decline require referral to a specialist.
The initial workup should include cognitive screening and assessment for depression, sleep apnea, substance use, and vascular risk factors.
What Researchers Still Don’t Know
Researchers do not yet know whether early cellular changes from repetitive head impacts inevitably progress to CTE, and reliable biomarkers for diagnosis in living patients are not yet available. Researchers are also figuring out why some patients with extensive exposure have no cognitive impairment or how cardiometabolic disease influences progression.
The Takeaway
Severe CTE is associated with dementia risk, while early pathology is not. Behavioral or psychological symptoms alone are not sufficient for diagnosis, and former athletes require a full dementia assessment. Early screening and vascular risk management remain crucial to care, and counseling should be individualized.