CTE was nearly ubiquitous among former NFL players who donated their brains to science
In a group of more than 100 professional football players whose brains were examined after their death, new research has found that virtually all suffered from chronic traumatic encephalopathy, a condition likely brought on by repeated blows to the head.
At a Boston University program that investigates the trauma-linked brain disease, researchers found that, of 111 former players for the National Football League who donated their brains for post-mortem examination, 110 bore the distinctive tangles, plaques and protein clumps now recognized as the neural hallmarks of CTE.
In life, all had suffered at least one of a range of behavioral symptoms — from mood instability and impulsiveness to substance abuse and aggression — that appeared to vary according to an athlete’s age at death, duration of participation in football and level of play. And the loved ones of the majority of the study’s participants told researchers that symptoms of CTE had worsened over the course of the participant’s life.
In nearly 9 out of 10 of those professional athletes — 86% — researchers found the telltale brain abnormalities of CTE were extensive, varied and scattered throughout the brain.
The report, published Tuesday in the journal JAMA, relates the accumulated findings from researchers’ post-mortem examinations of 202 brains, all donated by former football players or their families. Of those, researchers found clear evidence of CTE in 177, or 87.6%, of the brains they examined.
On average, those 177 athletes had played football for 15 years.
The study’s authors, led by Boston University neuropathologist Ann McKee, cautioned that the study does not suggest that severe traumatic brain damage would be found so widely in all who have played football.
The 202 brains examined in the study are called a “convenience sample.” They were donated, typically, by families after witnessing troubling symptoms that often progressed among players. In many cases of suicide, for instance, donor families strongly suspected that trauma-related brain damage had led to their loved one’s death.
Suicide was the most common cause of death among those diagnosed in the study with mild CTE, accounting for 27% of those deaths. The most common causes of death among those diagnosed with severe CTE were degenerative diseases such as Alzheimer’s and Parkinson’s disease. Close to half — 47% — of those with signs of severe CTE died of those causes.
In addition, the study did not compare the brains in the convenience sample to the brains of former football players chosen randomly or those who had no neuropsychiatric symptoms.
Not all the study’s participants played football professionally, and the findings of CTE also weren’t limited to NFL players.
Fourteen of the 202 donated brains came from football players who either did not live or did not play past high school, and three of those were found to have CTE.
Fifty-three of the study’s brains were donated by men who had played football at the collegiate level, and CTE was found in 48 of those.
Of 14 participants who had played semiprofessional football, nine had CTE. And seven of eight men who had played in the Canadian Football League were found to have the condition.
Half of all the 202 donors whose brains were examined had died before they were 66 and half after their 66th birthday. Researchers concluded that, over the whole sample, the severity of CTE tracked closely with the age at which the subject died, with older donors showing, on average, the clearest and most extensive signs of CTE.
Researchers distinguished between brains with “mild” pathology — 44 of the 177 that showed signs of CTE — and those with “severe” levels of the disease’s structural hallmarks — 133 of the 177 brains examined. On average, those with mild CTE had played football for 13 years. Those found to have severe abnormalities had played football for an average of 15.8 years.
The authors of the study found no clear patterns in players’ positions — offensive and defensive linemen and running backs were most prominently represented in the sample and among those diagnosed with CTE.
Researchers underscored that their study could not or did not gather data on other factors that may affect both the risk of developing CTE and the severity of the disease. Among those potentially influential considerations: age at first exposure to football and cumulative hits — both factors that are under study elsewhere.
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