At Least One in Four Former NFL Players Who Died Between 2016 and 2021 Had the Progressive Brain Disease CTE, Study Suggests

The true prevalence of CTE among the deceased NFL players might be much higher. Those with first-hand experience agree. CTE is believed to be caused by repeated head injuries, such as those endured in contact sports like football, hockey, soccer, wrestling and martial arts.

Symptoms like memory loss and mood swings can hint that someone might have CTE. However, the disease can only be diagnosed after death during an autopsy, when pathologists look for specific physical changes in the brain associated with CTE. CTE was first diagnosed in a former NFL player in 2005.

Since then, it’s been confirmed via autopsy in more than 300 athletes who were previously in the league. However, until now, researchers hadn’t been able to determine how widespread the disease might be—in other words, how common is it? To figure that out, scientists considered the 1,712 former NFL players—individuals who participated in at least one NFL game—who died between 2008 and 2021, 338 of whom had their brains donated for research purposes.

However, these organs could create a skewed sample, since families might be more likely to donate brains of athletes who experienced cognitive problems and therefore had CTE. So, the team zoomed in on former player deaths between 2016 and 2021, when brain donation was most frequent. Of the 878 individuals who died during that period, 235 had their brains donated for analysis, and 215 were found to have CTE.

Special statistical methods helped the researchers account for the unstudied brains and potentially skewed sample of analyzed brains, yielding an estimated CTE prevalence range. At a minimum, 24.5 percent of players who died during the study period had CTE, and at a maximum, 97.7 percent had the disease, the researchers calculated. The true prevalence probably falls somewhere in the middle.

For comparison, past research has found that CTE affects less than 1 percent of the general population. The new work is “significant,” says Randall Chesnut, a neurological surgeon at the University of Washington who wasn’t involved in the study, to NPR’s Becky Sullivan. It’s well controlled within the limits of the statistical analysis that they can pull off on this.” The findings should serve as a “wake-up call” for the NFL, lead author Daniel Daneshvar, a physician at Mass General Brigham and a brain injury researcher at Harvard Medical School, says in a statement.