HALIFAX - Dozens of Canadian soldiers say they suffered mild traumatic brain injuries while serving in Afghanistan, according to the first data collected by the military on what's been called a signature injury of the conflict.
The report, prepared for the military's surgeon general and obtained by The Canadian Press, shows that 6.4 per cent of the 1,817 soldiers surveyed from last January to May 2009 said they experienced a concussion while deployed.
It's the first time the Forces have tracked the injury, which has become a trademark of the wars in Afghanistan and Iraq due to the high rate of exposure to roadside bombs that can jar the brain and cause long-term health problems.
"The numbers are not surprising for me - the IEDs do occur, people are exposed and there are lot of near misses," Lt.-Col. Rakesh Jetly, a psychiatrist with the Forces' Directorate of Mental Health, said in an interview.
"I think the numbers are quite reasonable."
Most of the injuries were mild, with the majority of members recovering within days or weeks. Four people in the group said they lost consciousness for more than 20 minutes.
The bulk of the soldiers who reported a mild traumatic brain injury, or MTBI, said it was the result of a blast exposure, while others listed the cause as either a fall, fragment wound, motor vehicle accident or bullet.
About nine per cent of the members screened said they immediately suffered three or more symptoms, such as headaches, dizziness, irritability and depression - with some reporting effects lasting well after returning home.
But Jetly said the symptoms after a blast or other traumatic event can be so general and vague that they might be indicative of both mental health problems or a brain injury.
"The real difficult thing is to tease out the actual proportion of symptoms that are solely attributable to the shaken brain versus the psychiatric aspects," Jetly said.
"Where we're facing the real challenge is if someone six months later is complaining of symptoms like difficulty sleeping, irritability or headaches, how can we with certainty attribute that to the head injury?"
The question has spurred a global debate in the medical community about diagnosing and treating injuries that usually have their roots in a combat blast, but may be linked to two different diagnoses.
For example, Jetly said a soldier who is exposed to an improvised explosive device, or IED, may return and complain of headaches, sleeplessness, anxiety and fatigue.
They may chalk it up to a brain injury, when they may in fact be suffering from a mental health ailment, like post-traumatic stress disorder, or PTSD.
The report found that 84 per cent of those who reported "post-concussive symptoms" did not suffer a concussion.
A 2008 study in the New England Journal of Medicine found that "one must use caution when attributing health problems to mild traumatic brain injury, because associated PTSD and depression may be the primary problem."
Distinguishing the two is important for doctors and researchers who have to provide the right treatments and track any trends in the military that could lead to changes in gear or practices.
The Canadian data was gathered three to six months after the members returned home and were given a questionnaire that was updated in 2008 to include queries about brain injuries.
Jetly admitted that could affect the accuracy of the numbers since people might not properly recall their experience well after it happened overseas.
The Canadian military screens people in theatre after they've been exposed to a blast and will sideline them until they recover, said Jetly. When they get home, they're also checked for memory and concentration problems and can be referred for further evaluation.
A U.S. Department of Defence study indicated 140,000 U.S. soldiers deployed to Iraq and Afghanistan have been diagnosed with traumatic brain injury between 2001 and October, 2009.
That makes up about seven per cent of all U.S. personnel sent to the countries.
Experts researching the issue say they need to look at the issue of how repeated exposures affect the brain over the long-term and whether there is any link to conditions like dementia.