Brain Disease Prevalence: 75% of Deceased NFL Players Had CTE

An estimated 75 percent of former NFL players who died between 2008 and 2023 had chronic traumatic encephalopathy, according to a study released Wednesday. The research team, comprising scientists from Boston University, Mass General Brigham, and the Concussion & CTE Foundation, published their findings in JAMA Network Open. This marks the first comprehensive attempt by researchers to determine the prevalence of the neurodegenerative disease among deceased former professionals in the league.

The study analyzed 2,362 individual cases. Researchers combined data from 396 players who donated their brains with National Death Index records for 1,966 deceased players who did not. Nearly 94 percent of the donated brains showed signs of CTE. The paper noted that donors were more likely to be white, die at a younger age, and have longer NFL tenures compared to non-donors. Despite these demographic differences, the authors stated that the prevalence remained high after accounting for the variation in brain donation.

Chronic traumatic encephalopathy is currently diagnosable only after death, though ongoing research aims to identify tests for living patients. The disease is categorized into stages I through IV based on severity. The paper explained that many cases may have been in early stages at the time of death and possibly asymptomatic. Julia Gallini, the lead author, described the nearly 75 percent estimate as concerning in a statement. She emphasized the need for greater efforts to support families, diagnose the condition during life, and treat related symptoms.

Previous studies on CTE faced criticism for selection bias due to their reliance on brains donated by players who likely exhibited symptoms while alive. This new work addresses those concerns by including a large cohort of non-donors. The authors cautioned that the findings apply strictly to deceased NFL players and do not predict prevalence among living athletes. The study also does not address college or youth football levels, where data on non-donors remains limited.

The NFL responded to the findings by saying the league continuously strives to make football safer, including through strategies to reduce concussions and head impacts. The league encouraged former players to use available resources to identify and seek treatment when concerned about their health. The NFL Players Association stated that such studies are critical to improving the understanding of football's long-term impacts on players.

The new findings stand in contrast to an earlier paper by some of the same researchers published in August. That previous study estimated that only one in four former NFL players who died between 2016 and 2021 had CTE. The disparity highlights the shift toward a broader dataset in this latest analysis. Questions remain about how the disease manifests in lower levels of play, including high schools and colleges, where researchers noted a lack of data on non-donors.