At least 24.5% [1] of former National Football League players who died between 2016 and 2021 had chronic traumatic encephalopathy (CTE) [1].
The findings highlight the persistent risk of degenerative brain disease associated with professional football and may influence future safety protocols and health policies across the sport.
Researchers examined 235 [2] brains from a total of 878 [3] deceased NFL players who died during that five-year window. Of the brains studied, 215 [4] were diagnosed with CTE [2]. This data suggests that roughly one-quarter of the player population during this period suffered from the condition [1].
The study aimed to quantify the prevalence of the disease to better inform discussions regarding player safety in the U.S. [1]. CTE is a progressive brain disease found in people with a history of repetitive brain trauma, including symptomatic hits to the head.
Other data points provide a different perspective based on the nature of the samples. A report indicated that 91.4% [5] of all donated brains studied between 2016 and 2021 were diagnosed with CTE [5]. This higher percentage reflects a selection bias, as families are more likely to donate the brains of players who showed symptoms of cognitive decline before they died.
The NFL Players Association said the findings should be a call to action across the entire football ecosystem [6]. The discrepancy between the general deceased population and the donated sample underscores the difficulty of calculating exact prevalence rates in the living.
“At least 24.5% of former National Football League players who died between 2016 and 2021 had CTE.”
The gap between the 24.5% prevalence rate and the 91.4% rate among donated brains illustrates a significant 'selection bias' in CTE research. While the lower number provides a more realistic estimate of the general player population, the higher number shows that the disease is overwhelmingly present in players who exhibit neurological symptoms. This data reinforces the link between repetitive head impacts and long-term brain decay, placing further pressure on the NFL to implement more stringent concussion and head-impact rules.
