Boston study estimates 75% of late NFL players showed CTE signs

Researchers at Boston University analyzed the brains of 387 deceased former NFL players to estimate the prevalence of chronic traumatic encephalopathy, or CTE. The team concluded that approximately 74.5% of former players who died between 2008 and 2023 likely had the condition.

The study, published in JAMA Network Open, examined a subset of the 2,362 former NFL players who died during that 15-year period. Ninety-four percent of the donors whose brains were examined showed some form of CTE. To account for the fact that players with cognitive symptoms are more likely to donate their brains, the researchers calculated that such individuals were five times more likely to be donors. They used this ratio to estimate the broader population rate.

Dr. Jon LaPook, CBS News chief medical correspondent, cautioned that the figure may overestimate the actual rate. He noted the study measured signs of the disease in brain tissue rather than clinical symptoms in living patients. The findings build on earlier data from The British Medical Journal, which reported that 98% of ex-NFL players who died between 2016 and 2021 had CTE.

Dr. Kristen Dams-O'Connor, director of the Brain Injury Research Center at Mount Sinai, stated that the results should not be interpreted as representative of current living athletes. She pointed out that many of the studied players ended their careers long ago. The NFL has implemented rule changes and introduced more protective equipment in recent years to reduce concussions and head impacts.

"This should translate to lower CTE risk in recent generations of players, compared to those who played decades ago," Dams-O'Connor said. She also noted gaps in the data, including the approximately 20,000 NFL players who may have died during the study period but were not included. She added that the results do not apply to the vast majority of people who played youth football or other non-professional contact sports.

Dr. Jeremy Tanner, assistant professor of neurology at The Glenn Biggs Institute for Alzheimer's and Neurological Diseases at UT San Antonio Health Science Center, called the study helpful for understanding the bigger picture. He said that even after adjusting for selection bias, a minimum rate of 20 to 25% is eye-opening and demonstrates the need to advance research.

Dr. Jay Alberts, director of the Cleveland Clinic Concussion Center, argued that the data highlights the need to look for early warning signs. He suggested that monitoring instrumental activities of daily living, such as driving or balancing a checkbook, could reveal brain function changes before a formal diagnosis. These skills require simultaneous cognitive and motor function, and changes in them often appear five to seven years before diagnoses of other neurodegenerative diseases.

Tanner said that ongoing studies, including one at UT Health San Antonio, follow current and former players to track biomarker changes over time. He expressed hope that these tools will enable doctors to detect brain changes during life, allowing for better prevention or treatment of diseases like CTE, Lewy body disease, and Alzheimer's.