Scientists from the United States and England say brain tissue in four American military members showed signs of chronic traumatic encephalopathy, or CTE, a progressive disease normally linked to repetitive concussions.
The condition has been identified in more than a dozen professional football players who have died after suffering multiple concussions. In some cases, they developed memory loss, irritability, dementia and suicidal thoughts before they died.
Patric Stanton, a cell biologist at the New York Medical College, said the international team of scientists found telltale signs of the disease in veterans exposed to even just one blast from an improvised explosive device, a weapon that became the hallmark of the Afghanistan conflict.
"This is really the first demonstration that their brains look indistinguishable from that you see in athletes that have had multiple concussions," he said upon the release of the findings Wednesday in the online journal, Science Translational Medicine.
"It's very worrisome."
The researchers, based largely at Boston University, looked at the brains of four veterans after they had died, three of whom had been exposed to IEDs.
The fourth had suffered concussions in and outside the military and developed post-traumatic stress disorder, but didn't have a blast exposure.
He said they all showed signs of CTE and that it may only take one blast exposure to develop symptoms, rather than multiple hits to the head suffered by some athletes who have the condition that is characterized by abnormal protein deposits.
"It's as if the blast has concentrated in a second or so repeated concussions — like a whole NFL career might be concentrated in a few seconds," he said.
The researchers said they found that the blast produces a wind that can reach a velocity of 530 kilometres per hour and moves the person's head back and forth very rapidly, causing the brain to get compressed several times as it floats in fluid.
They recreated the effect in mice and discovered signs of the disease only two weeks after exposing them to a single blast.
The blasts can cause traumatic brain injuries, which can lead to symptoms that are thought to be short-lived, depending on the severity of the blast.
Thousands of military members in Canada and other countries have been exposed to the potent blasts from IEDs, the crude bombs that maimed and killed dozens of Canadian Forces in Afghanistan over the course of the 10-year mission.
It's estimated that just over five per cent of personnel deployed to Afghanistan from 2009 to 2011 experienced a mild traumatic brain injury.
Col. Rakesh Jetly, a senior Canadian Forces psychiatrist, said he had read the Boston University report and was awaiting further details on the research. He added that the Canadian Forces has created a special panel on managing brain injuries in the military.
"The Canadian Forces Health Services is constantly studying evidence-based research related to blast exposure and seeking ways to improve care to personnel suffering from brain injuries," he said in an emailed statement.
A report from November 2009 found that 6.4 per cent of Canadian Forces members deployed to Afghanistan had experienced mild traumatic brain injury.
The military reported that the vast majority of those screened weren't showing symptoms three to six months post-deployment.
But Stanton says the progression of disease can take years to play out.
"So when the military assures people that all your symptoms will be short-lived and you will be fine, they have no basis on which to prove that," he said.
The scientists compared the veterans' brain tissue to that of young football players and a wrestler who had suffered repeated concussions. They found disturbing similarities between the two groups.
"Our study provides compelling evidence that blast traumatic brain injuries and CTE are structural brain disorders that can emerge as a result of brain injury on the battlefield or playing field," said Lee Goldstein, associate professor at Boston University School of Medicine and the report's lead author.
"Now that we have identified the mechanism responsible for CTE, we can work on developing ways to prevent it so that we can protect athletes and our military service personnel."