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Despite the high risk of brain injury, military personnel rarely develop chronic traumatic encephalopathy (CTE), a disabling condition often found in former boxers and soccer players.
Less than 5% of the 225 brains of dead service members showed evidence of CTE, a team reported in the June 9 issue. New England Journal of Medicine.
In contrast, a 2017 study of the brains of dead college and NFL football players found that 87% had symptoms of CTE.
Even service members who had experienced injuries from the bombing were less likely to develop CTE. Only 6.7 percent of the brains of 45 people exposed to the blast were diagnosed with the condition.
The results indicate that “serving in the military and exposure to explosions is probably not a significant risk factor for CTE development,” said Dr. Daniel Pearl, professor of pathology at Bethesda Uniform Services University and one of the study’s authors.
CTE can only be diagnosed after a person has died. During an autopsy, a pathologist looks for areas of the brain where there is a high concentration of protein toxins.
This condition is associated with dementia, mood problems and various mental disorders.
The CTE’s symptoms overlap with those of military personnel exposed to the bombings.
So some doctors are concerned that CTE may be partly responsible for the high rates of suicide and post-traumatic stress disorder (PTSD) among veterans working in Iraq and Afghanistan.
“Their families say their personalities have changed, they are having trouble sleeping,” Pearl said.
To see if CTE was a factor, the researchers turned to the Brain Tissue Repository, which is run under the direction of the Department of Defense and Uniform Services University Pearl.
“We said it was an opportunity to look at these brains and see how much CTE has played a role in this problem,” Pearl said.
The team found that only three of the CTE’s 10 brains came from service members who were the victims of the bombing.
“Then we saw that all ten played a communication game,” Pearl said.
The results add evidence that bomb blasts and the effects of sports affect the brain in different ways.
In football or boxing, a brain injury is caused by an impact that pushes the brain against the skull. In a bomb blast, a pressure wave travels through the brain tissue, causing it to expand and deform.
“Physics is different,” Pearl says. “And apparently the pathology that comes from it is different.”
But both impact and explosion can cause long-term damage, Pearl says.
“One should not shy away from thinking that we have not found CTE, the brain is normal,” he said. “This is clearly not the case.”
Also, most of the brains in this study came from relatively young people, Pearl said. So it is possible that they could develop CTE at a much older age.