A significant portion of former NFL players who passed away between 2016 and 2021 were found to have a degenerative brain disease. Researchers examined the brains of players who died during this period and donated their brains to research. The majority of donated brains showed signs of the disease.

This condition can only be confirmed after death, making brain donation crucial for research. A study published by the British Medical Journal revealed the findings, which are based on a specific group of players. The study's lead author notes that the reported percentage is likely an underestimate.