Chronic brain disease affected at least one in four deceased football players

A study of former professional athletes estimates that between a quarter and nearly all who died across six years had chronic traumatic encephalopathy, driven by cumulative head impacts.

The physical toll of contact sports accumulates quietly over decades. An athlete absorbs thousands of routine collisions and jarring hits across youth leagues, high school rosters, and collegiate teams before ever taking a snap in professional competition. Each impact jostles delicate brain tissue inside the skull, creating microscopic mechanical trauma. Over time, that repeated structural stress can initiate a progressive breakdown of neurological tissue known as chronic traumatic encephalopathy, or CTE. Because physicians can only diagnose the condition by examining brain tissue under a microscope after death, measuring how widely it spreads across former athletes has remained a persistent challenge.

A study published in the British Medical Journal provides new boundaries on how common the degenerative condition was among professional players who died in recent years.¹ Daniel Daneshvar, an associate professor at Harvard Medical School, led an investigation into the records of 878 former National Football League players who died between 2016 and 2021.¹

The paper reports that former NFL competitors face an elevated mortality burden from brain disorders compared with the broader public. Daneshvar noted that previous research from his group and other teams demonstrated about a four times higher rate of death from neurodegenerative disease among NFL players than the general population.¹ The new analysis aimed to determine how many deceased players actually had the underlying pathology of CTE at the time of their deaths.

How common was the disease among deceased players?

Researchers determined that at least 24.5 percent of the 878 former NFL players who died during the six-year period had chronic traumatic encephalopathy.¹ Among the total group of 878 deceased athletes, families donated the brain tissue of 235 individuals to scientific research. Laboratory examinations confirmed CTE pathology in 215 of those 235 donors, while dementia was also common across the examined group.¹

To estimate the true prevalence across the entire cohort of 878 players, Daneshvar and his colleagues calculated mathematical bounds. If every single one of the 643 players whose brains were not donated had zero brain disease, the prevalence among the deceased cohort would sit at the conservative minimum of 24.5 percent. If the unexamined players experienced the disease at the same rate as the donors, the prevalence would reach a calculated maximum of 97.7 percent of the deceased cohort.¹ Daneshvar stated that these findings indicate NFL players carry a higher prevalence of CTE at death than community-based studies have previously demonstrated.¹

Where does the underlying brain damage occur?

The vast majority of the repetitive head impacts that elevate disease risk occur before athletes ever enter the professional ranks. An individual athlete plays years of tackle football in childhood, adolescence, and early adulthood, absorbing hundreds of head impacts in practice sessions and competitive games each season.

Daneshvar emphasized that the cumulative volume of these hits over a lifetime drives the risk.

The bulk of the head impacts that these former NFL players experienced didn't occur at the NFL level. They occurred at the collegiate level and at the high school level and in many cases the youth level. And all of those cumulative hits to the head added up to result in an increased risk.

What can these post-mortem findings tell researchers?

The results represent a post-mortem observational study of brain donors, rather than a prospective health measurement of living people. Because brain tissue can only be evaluated after death, researchers cannot use this methodology to screen active players or predict individual clinical outcomes during a player's lifetime.

The figures also reflect self-selection in tissue donation. Families of former players who showed signs of cognitive decline, depression, or behavioral changes during life are more likely to donate tissue to research banks than families of players without symptoms. This donation pattern means the 235 examined brains do not represent a purely random sample of former players. The calculated range between 24.5 percent and 97.7 percent accounts for this uncertainty by modeling the absolute lowest and highest possibilities for the unexamined players.

What comes next for player safety and football governance?

The findings have prompted the researchers to urge football governing bodies to implement stronger prevention policies to minimize head impacts at every level of the sport. CTE has become a central medical and legal issue for football over the past decade. The NFL acknowledged a link between football and degenerative brain disease in March 2016, following a 2011 Collective Bargaining Agreement that limited full-contact practice sessions.¹ The league also agreed to a settlement valued at 1 billion dollars, or about 700 million pounds, with more than 5,000 former players after a prolonged class-action lawsuit.¹

Responding to the new research, an NFL spokesperson stated that the organization continuously strives to make football safer by implementing strategies designed to reduce concussions and head impacts. The spokesperson added that the league remains committed to expanding resources for physical and mental well-being and encouraged former players to seek medical evaluation when concerned about their health. Future research faces the task of identifying clinical biomarkers in living athletes and evaluating whether ongoing youth rule changes successfully reduce the long-term burden of neurodegenerative disease.

Reporting note: This piece was prepared from the paper in the British Medical Journal and public records; the authors have not been interviewed.

References

This article is based on 1 source, listed in the order they are cited.

1. 1 BS BBC Sport announcement · 25 Aug 2026 NFL: At least one in four dead players had brain disease, says study See the source