Study: At least 25% of NFL players may develop brain disease

A significant portion of National Football League (NFL) players, at least one in four, may develop a degenerative brain disease, according to a new study published Tuesday. The research highlights the profound toll American's favorite sport can take on its athletes.

Chronic Traumatic Encephalopathy (CTE), caused by repeated head impacts, manifests in symptoms such as cognitive decline, walking difficulties, emotional instability, and suicidal thoughts. While previously linked to contact sports like American football and boxing, and even military personnel exposed to explosions, CTE can only be definitively diagnosed post-mortem.

The study, led by Daniel Daneshvar of Harvard Medical School and published in the British Medical Journal, examined the brains of deceased players who participated in at least one NFL game during the era of mandatory plastic helmets, starting in 1949. The most substantial findings came from individuals who died between 2016 and 2021, a period with more frequent brain donations.

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In aggregate, these findings indicate that NFL players have a higher prevalence of CTE at death than has been shown in multiple prior community-based studies.

Out of 878 deaths during this timeframe, 235 brains were donated for examination, and CTE was confirmed in 215. This indicates a minimum CTE rate of 24.5%, assuming none of the unanalyzed brains contained the disease. The maximum estimate reached 97.7%, with the actual figure likely falling somewhere in between. Researchers also observed a correlation between high-grade CTE and dementia, based on players' medical records and family interviews.

"In aggregate, these findings indicate that NFL players have a higher prevalence of CTE at death than has been shown in multiple prior community-based studies," the authors wrote. They added, "These data indicate that the severity of CTE at death is significantly associated with dementia in NFL player brain donors, and that dementia is frequent in these donors." However, the study acknowledges limitations, including incomplete inclusion of all deceased NFL players from the study period and potential inaccuracies in family recall.

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These data indicate that the severity of CTE at death is significantly associated with dementia in NFL player brain donors, and that dementia is frequent in these donors.