CTE risk strongly linked to duration of American football play, study reports

In a study that analyzed 266 former football players, researchers discovered that risk of chronic traumatic encephalopathy doubled for every 2.6 years of play.

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In a study published in Annals of Neurology, a team of researchers reported that a player’s risk of developing chronic traumatic encephalopathy (CTE) increased by 30% with every year they participated in American football. 

The research team from the Boston University CTE center (MA, USA) analyzed the neuropathology of 266 deceased American football players to evaluate the association between CTE and years of football play. 

A total of 223 out of the 266 participants met the diagnostic criteria for CTE. Those who did not meet the criteria formed a large enough control group to provide a sufficient amount of data to increase the researcher’s confidence in the strong relationship discovered. 

         This study is a testament to the hundreds of families who have donated their loved one’s brain. It is only because of this support that we can confidently estimate the strength of the relationship between duration of [football] play and risk of CTE,” commented study author, Ann McKee (Boston University). 

The large amount of brain donations has provided the researchers with a large enough sample size to draw statistically relevant conclusions from their analysis. 

         While we don’t yet know the absolute risk of developing CTE among American football players, we now can quantify that each year of play increases the odds of developing CTE by 30 percent,” explained lead author, Jesse Mez (Boston University). “We hope that these findings will guide players, family members, and physicians in making informed decisions regarding play.”

The team discovered that those who played football for fewer than 4.5 years were ten times less likely to develop CTE compared with those who played longer. However, researchers noted that several players with football careers longer than 15 years did not have evidence of CTE, demonstrating that there are exceptions. 

The average length of a player’s career in the National Football League is 3.3 years, however, the number of athletes who have had premature and sudden retirements suggest that more attention should be placed on the impact the game has on their health. 

A limitation of CTE research is that brain donors may not be representative of the wider population, limiting how much the findings can be generalized. Confounding factors may bias the relationship being invested, nevertheless, the research team were able to demonstrate that the findings remained consistent even after they factored in potential confounders. 

Currently, CTE can only be diagnosed after death, Mez commented: 

“       These findings move us closer to diagnosing CTE in life, which is critical for testing potential therapies and for guiding clinical care.”

Sources: Mez J, Daneshvar DH, Abdolmohammadi B et al. Duration of American football play and chronic traumatic encephalopathy. Ann. Neurol. doi:10.1002/ana.25611 (2019) (Epub ahead of print); www.bu.edu/articles/2019/cte-football/

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