Study finds 74.5% of ex-NFL players had CTE

A new study estimates that 74.5% of deceased former NFL players had chronic traumatic encephalopathy.

The research team analyzed data from 2,362 former professional football players who have died. The study appeared in the Journal of the American Medical Association on Wednesday. Of the total group, 396 players donated their brains for examination. The remaining 1,966 players did not donate their brains.

Among the brains that were examined, 93.5% showed signs of CTE. Researchers adjusted this raw number to account for differences in who donates brains. They estimated that families were about five times more likely to donate a brain if they had noticed cognitive symptoms in the player during his life. After this adjustment, the estimated prevalence rate stood at 74.5%. Yorghos Tripodis, a professor of biostatistics at Boston University and an author of the paper, stated that the estimate does not drop below 60% even under very conservative assumptions.

The study also looked at dementia rates. Researchers estimated that 27.2% of the former players had dementia during their lifetime. The team noted that this figure likely underestimates the true prevalence of the condition. Tripodis explained that the earlier study from August could only provide a range between 25% and 98%. The new work aims to provide a more precise answer to that wide variance.

The NFL responded to the findings with a statement. The league said it continuously strives to make the game of football safer. It cited strategies to reduce concussions and head impacts. The statement also noted that the organization remains committed to ensuring the NFL community has access to resources for physical and mental well-being. The NFL Players Association told ABC News that the August study was a sobering reminder of the real risks in football. The union said the risks can have lasting consequences for players and their families. It reinforced the priority of improving player safety and supporting players throughout their lives.

CTE is a brain disease associated with repeated head impacts. The Centers for Disease Control and Prevention describes it as a buildup of abnormal proteins that damage brain tissue. This process can cause brain cells to die. The disease can only be confirmed through an autopsy. Families must donate the brain of a loved one for researchers to examine the tissue.

Commissioner Roger Goodell announced the Play Safe, Play Smart initiative in September 2016. The organization pledged $100 million to player safety at that time. Goodell described the initiative as a way to drive progress in the prevention, diagnosis, and treatment of head injuries. He also said it aims to enhance medical protocols and improve how the game is taught and played.

The researchers cautioned that their findings apply specifically to deceased former NFL players. They noted that the results may not be representative of living NFL players. Betsy-Ann Assoumou, a family medicine resident at Dartmouth Health, is a member of the ABC News Medical Unit.