(RxWiki News) About 10 million people experience a mild traumatic brain injury across the world each year. Understanding risk factors for these injuries may help with prevention.
A recent study investigated possible common factors linked to mild traumatic brain injury among a large group of military men.
The researchers found that men who experienced a mild traumatic brain injury were much more likely to have a lower cognitive function (such as IQ) than men who were not injured.
But this lower cognitive score was seen before the men had the traumatic brain injury. Therefore, the lower cognitive function might be a risk factor itself for mild traumatic brain injury.
"Protect your head - wear a helmet."
The study, led by Anna Nordstrom, an associate professor at the Department of Community Medicine and Rehabilitation at Umeå University in Sweden, aimed to understand risk factors for mild traumatic brain injury.
Mild traumatic brain injury results from an injury to the head which can lead to difficulties with attention, memory, verbal learning and the ability to think quickly.
The researchers collected data from the medical records of 305,885 men who were enlisted in the Swedish military between 1989 and 1994.
All these men underwent physical exams and standardized intelligence tests before they were assigned their post in the Swedish Armed Forces.
The researchers looked at the results of these assessments and considered other factors, such the men's age, weight, hearing and vision, in looking for possible patterns related to traumatic brain injury rates.
The researchers found that the 1,988 men who experienced one mild traumatic brain injury within the two years before their testing had an average 5.5 percent lower brain function scores than the men who had no mild traumatic brain injuries.
The 2,214 men who had a mild traumatic brain injury within the two years after their cognitive function test also had about 5.5 percent lower cognitive function scores than men without brain injuries.
Men who had at least two mild traumatic brain injuries within two years of being tested had approximately 15 percent lower cognitive function scores the first time they were tested (before injury) compared to men without a brain injury.
These findings mean it is possible that some men who have a mild traumatic brain injury might show lower cognitive function because they started out with lower function, not just because they sustained an injury.
The researchers tested this findings in the study by also looking at the pairs of twins included in the study groups.
"We investigated cognitive function in twin pairs in which only one of the twins had a mild traumatic brain injury before cognitive testing," the authors wrote. "Both twins had lower logical and technical function compared with men in the total cohort with no mild traumatic brain injuries. Our data indicate that genetic factors and a similar environment explain the lower cognitive function found in these twins."
Even when only one twin had fought in battle, the cognitive function of both was similar.
"In support of our results, cognitive deficits and structural abnormalities of the brain were found in both twins when only one had been exposed to combat exposure and developed a post-traumatic stress syndrome," the authors wrote.
The most common causes of mild traumatic brain injuries among the men were falls, assault and trauma during transportation, such as car accidents.
The researchers identified some other risk factors that appeared to correlate with a person's risk of mild traumatic brain injury. These factors included overall cognitive function, a past mild traumatic brain injury, having been admitted to the hospital for drunkenness, a low level of education and a lower socioeconomic status.
The study was published March 12 in the journal BMJ. The research was funded by the Swedish Research Council. The authors declared no conflicts of interest.