EL PASO — A study published in The BMJ found that 315 of 338 brain donors who were former NFL players had chronic traumatic encephalopathy. Researchers advised that people playing American-style football be warned of the risks of repeated head injury.

The analysis covered 1,700 former National Football League players who died between 2008 and 2021. Of those deceased athletes, 338 donated their brains for neuropathological evaluation.

Neuropathologists masked to clinical and playing histories evaluated postmortem chronic traumatic encephalopathy diagnosis and stage. This masking ensured that the evaluators did not know the medical backgrounds or specific playing records of the donors during their assessments.

The results showed that 315 of the 338 brain donors had a diagnosis of chronic traumatic encephalopathy. This figure represents 93.2% of the individuals who provided brain tissue for the study.

Approximately 31% of the brain donors had stage 4 chronic traumatic encephalopathy. This advanced stage of the disease indicates severe neurodegeneration and significant accumulation of pathological proteins in the brain.

Approximately 60% of the brain donors had clinician-diagnosed dementia with an age of onset at 63.4 years. The early onset of cognitive decline suggests a strong link between the neurodegenerative process and the clinical symptoms observed in life.

More than 90% of donors with stage 4 chronic traumatic encephalopathy had dementia at death. This high correlation reflects the severity of the condition in its most advanced form.

The lesion present in chronic traumatic encephalopathy is a perivascular accumulation of hyperphosphorylated tau in neurons at the depths of the cortical sulci. This specific pathological signature distinguishes the disease from other forms of dementia and neurodegeneration.

Chronic traumatic encephalopathy can only be diagnosed via autopsy. Current imaging techniques for looking at tau are not specific enough to diagnose chronic traumatic encephalopathy in living patients.

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Rick Lange is the president of Texas Tech Health El Paso. Elizabeth Tracey is the director of electronic media for Johns Hopkins Medicine in Baltimore.

"What's the relationship between chronic traumatic encephalopathy and dementia?" Tracey said. Her question shows the ongoing need to clarify the clinical progression of the disease.

"And is there an association with ADHD and cardiovascular events in people with hypertension?" Lange said. This inquiry points to broader health considerations that may intersect with neurological conditions.

What's New

Approximately 25% of NFL players who died between 2016 and 2021 had stage IV chronic traumatic encephalopathy, according to a 2026 study published in The BMJ, indicating a significant increase in disease severity compared to earlier decades. This finding provides updated context on the progression of the disease in recent years.

A prior study published in The BMJ in 2017 found that 31% of former NFL players who donated their brains had stage IV chronic traumatic encephalopathy (CTE), similar to the current findings but based on a smaller sample size. The comparison helps establish trends in the prevalence of severe CTE over time.

Why It Matters

The study identifies a high prevalence of chronic traumatic encephalopathy among former NFL players who donated their brains, with 315 of 338 donors receiving a diagnosis. The researchers estimate that the prevalence among all deceased players in the study period falls between 18.5% and 98.7%, indicating a substantial burden of disease within this population.

Study authors advise that people playing American-style football should be warned that repeated head injury might result in an increased rate of chronic traumatic encephalopathy, dementia, and early death. This guidance addresses the public health implications of the sport and the need for informed consent regarding long-term neurological risks.