New research links CTE to 75% of dead NFL players

A new analysis of federal death records indicates that 74.5% of former NFL players who died between 2008 and 2023 likely had chronic traumatic encephalopathy, or CTE.

The study, published Wednesday in JAMA Network Open by researchers at Boston University, examined records for all 2,362 former players who died during that period. While CTE is a degenerative brain disease that can only be confirmed after death, previous studies relied heavily on donated brains. Those donations often came from families of players who already displayed memory or behavior issues, which can skew results upward.

To account for this bias, the research team used data from 396 brains donated to BU’s brain bank. They found that 93.5% of those examined had CTE. However, players showing cognitive symptoms were about five times more likely to have their brains donated. By adjusting for that selection bias, the researchers calculated that 74.5% of all deceased players had some stage of the disease. Their most conservative estimate placed the figure at 63.7%.

Yorghos Tripodis, a biostatistician at the Boston University School of Public Health and a lead researcher, noted that CTE is found in less than 1% of people who do not experience repetitive head impacts. He said the high prevalence in former football players should prompt action to improve safety.

The authors cautioned that many of these cases were likely in early stages and asymptomatic. The findings do not apply to living players or to individuals who played only in high school or college. Tripodis explained that while padded Guardian Caps worn over helmets protect the skull, they do not prevent the rotational movement inside the brain that causes CTE.

The NFL acknowledged a link between the sport and CTE in 2016 and has since updated rules and equipment. Tripodis suggested that reducing tackle football before high school and limiting it during practice could lower the main cause of the disease. Mike Vrabel, the New England Patriots coach and former NFL linebacker, said on Wednesday that he supports the league’s safety efforts but believes players understand the risks involved in playing the game.

The NFL Players Association stated in a release that such studies are critical for understanding the long-term impacts of football. The union said it will continue to support players and their families through programs like the Football Players Health Study at Harvard University.