An estimated three-quarters of former National Football League players who died across a 16-year period developed the devastating neurodegenerative disease chronic traumatic encephalopathy, or CTE, according to a population-level study published October 28 in JAMA Network Open by a Boston University research team.
A 2017 study from the same academic circle previously estimated that 99 percent of former NFL players developed the condition from an analysis of donated brains. However, that earlier figure carried a significant selection bias, as grieving families were far more likely to donate the brain of a relative who exhibited symptoms in life.
By adjusting for this potential distortion, investigators calculated a population-level estimate of 74.5 percent among deceased professional football players. The retrospective analysis evaluated every former NFL player who died between January 2008 and December 2023. The cohort of more than 2,300 players included almost 400 samples housed in the university’s UNITE Brain Bank, while researchers tracked the remaining individuals using records from the U.S. National Death Index.
In Plain English: The Clinical Takeaway
- What is CTE? Chronic traumatic encephalopathy is a neurogenerative disease linked to repeated blows to the head over time. It is diagnosed after death, during an autopsy.
- Why the drop in percentage? Prior research indicated a figure hovering around 99 percent since relatives of athletes displaying clinical signs of CTE while alive showed a fivefold increase in the likelihood of offering up their loved one’s brain. Adjusting for this bias yields the new 74.5 percent estimate.
- What are the cellular mechanisms? In CTE, a standard brain protein known as tau—which normally supports nerve cell signaling alongside other functions—malfunctions and forms abnormal, destructive aggregations.
The Pathology and Clinical Presentation of Repetitive Head Trauma
The development of CTE is linked to repeated blows to the head over time. While the condition has been identified most frequently among American football players, it can occur in people who play contact sports, experience intimate partner violence or engage in military combat. Research involving gridiron athletes indicates that extended periods of recurrent head injuries correlate with both an increased probability of developing CTE and greater severity of the disorder.
Individuals who eventually receive a postmortem diagnosis of CTE may suffer from various afflictions while living, such as memory problems, trouble maintaining focus, depressive moods and diminished self-regulation. At a molecular level, the disease involves brains being snarled with irregular, damaging clumps of the protein tau.
Accounting for Selection Bias in Brain Banking
To arrive at the 74.5 percent population-level estimate, the Boston University team quantified the skew within brain donation practices. Researchers calculated that relatives of former football players who exhibited CTE-associated signs while alive were five times more inclined to contribute their deceased kin’s brain compared to households whose members showed no such manifestations.
Accounting for this statistical skew was necessary to understand the true public health impact of the disease. Investigators emphasize that gauging the exact occurrence rate of CTE proves vital for grasping how severely the condition affects public health overall.
Contraindications & When to Consult a Doctor
Because the condition is diagnosed after death, during an autopsy, living patients cannot be clinically confirmed with the disease.
Future Trajectories in Neurodegenerative Research
Establishing an accurate population-level prevalence is important to understanding the public health impact of the disease.
