Post-mortem analysis of the brains of 111 deceased NFL players revealed that all but one had a neurodegenerative brain disease.
The brains exhibited chronic traumatic encephalopathy (CTE), a progressive degeneration. Scientists have linked repeated head trauma with the disease. Brains with this disease have a high amount of abnormal tau proteins, which block neuropathways. This can, in turn, lead to aggression, impaired judgment, depression, anxiety, memory loss, impulse control problems, and confusion. Individuals may suffer from suicidal tendencies as well.
In total, the study included 202 brains from individuals who played football on all levels. The brains belonged to players who had died as young as age 23 and as old as age 89. These individuals played football at high school, college, and semi-professional levels, as well as professionals who played in the NFL and the Canadian Football League (CFL).
The researchers discovered CTE in 177 of the 202 players. This surprised even the researchers, who did not expect that 87% of the subjects would have the disease.
Only an autopsy can lead to a formal diagnosis of the disease. Researchers have found people who play contact sports—American football in particular—comprise most diagnosed cases of CTE. This has led researchers to claim that football players are especially at risk of developing the disease.
This study on CTE is currently the largest ever of its kind. The brains in the study had been donated specifically for scientific research. Researchers selected brains according to a number of criteria, foremost of which was that playing football had to be the main cause of brain trauma. It didn't matter if the individual had exhibited symptoms of CTE in his lifetime, but he had to have experienced repeated head trauma.
Researchers also found that the likelihood of developing CTE varied depending on the individual's playing level. For example, only three of the 14 high school football players had CTE, and even these three had only a mild form of the disease. However, over half of those who played at the college and semi-pro levels suffered from a severe form of the disease.
Pro-level players weren't as lucky. Seven out of the eight CFL players also had severe CTE, and so did 110 of the 111 NFL players included in the study.
Given these findings, the researchers theorize that the longer an individual plays football, the more likely it is that he'll develop severe CTE. However, researchers still have more work to do to prove this theory true.
The researchers also made it clear that the findings aren't representative of all football players, living or dead. We have to consider the fact that the players' families had submitted the brains for research. It's possible that the players to whom the brains belonged had exhibited symptoms of CTE in life, which motivated their families to submit their brains for scientific study. Thus, this may have skewed the results.
In any case, we still can't discount the possibility that NFL players and other athletes who play contact sports are at risk of severe brain trauma. This, as one the study's authors said, is something that people can't ignore anymore.
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