New Study: 75% of Deceased NFL Players Likely Had CTE

A new study published Wednesday estimates that three out of four former NFL players who died between 2008 and 2023 most likely suffered from chronic traumatic encephalopathy, or CTE. This represents the highest prevalence estimate to date for the degenerative brain disease among deceased athletes.

The research team, based at Boston University’s CTE Center, combined data from 396 donated brains with national death records for 1,966 other deceased former players. They used these records to account for players who did not donate their brains, a group that often includes individuals with cognitive decline. This methodology aimed to provide a more accurate picture of the disease’s reach than previous studies that relied solely on autopsies.

The findings follow an April study by the same group, which examined 338 brains from players who died between 2016 and 2021. In that earlier analysis, 315 of the studied brains showed signs of CTE. The new report expands the timeframe and the sample size to reach its three-in-four conclusion.

In an emailed statement, an NFL spokesperson said the league continuously strives to make the game safer by implementing strategies to reduce concussions and head impacts. The league has also invested in growing flag football, a non-contact version of the sport that is gaining traction with youth leagues across the country.

Parents in Chicago and San Diego are citing these medical findings as a primary reason for moving their children away from tackle football. Sandeep Basran, an assistant coach in Chicago, keeps his 9-year-old son in a flag football league to avoid repetitive hits. Basran noted that his understanding of the research suggests minor, repetitive impacts accumulate over time to affect the brain.

Joe Becker, owner of i9 Sports in Chicago, said he is marketing flag football heavily to girls as the sport expands. Flag is the main outlet for girls to play football, and it is now an Illinois state sport for high schools. Becker expects continued growth as the sport prepares for its Olympic debut.

Data from the Aspen Institute’s State of Play report shows that between 2019 and 2024, flag football was the only team sport to grow among kids ages 6 to 17. During that period, flag participation rose by 14 percent while tackle participation fell by 7 percent. By 2024, 4 percent of children ages 6 to 12 played flag compared to 2.7 percent who played tackle.

However, the shift is less pronounced among older teens. For ages 13 to 17, tackle remains more popular, with 6.4 percent participation compared to 2.8 percent for flag. The report attributes flag’s growth among younger kids to NFL investment and parents delaying or abandoning tackle due to brain injury risks.

Tim Lewis, a parent and coach in San Diego, observes rapid growth in girls’ flag football. He coached boys for five years before taking on a girls’ team, which he says is where the sport is exploding. Lewis noted that local high schools are hosting games that draw large crowds of young players and fans.

The sport will debut as an official Olympic event at the 2028 Los Angeles Games. Rashad Crawford, a mentor for young players in Chicago, believes this visibility could lead to professional leagues within the next four to six years. He said kids in flag leagues are developing the same camaraderie and celebration culture seen in tackle football, planning specific team moves for touchdowns during huddles.

Robert Stern, a co-founder of the CTE Center, said he can no longer watch tackle football due to the medical risks. Stern, who has researched the disease for nearly 20 years, explained that humans are not built for repeated head impacts. He and his colleague Chris Nowinski, another co-founder, are authors of the recent studies. They noted that CTE is caused by a buildup of an abnormal protein called tau, which can begin decades after the initial hits.

There is currently no cure for CTE, and a definitive diagnosis can only be made after death. The Boston University CTE Center houses the UNITE Brain Bank, the largest collection of brains focused on trauma in the world. While concussions are a risk factor, Stern and Nowinski said a player can develop CTE even without a history of diagnosed concussions.