MONDAY, May 7, 2018 -- Concussions, even those that are mild, more than double the risk for developing dementia down the road, new research suggests.
The findings stem from an analysis that tracked concussions and dementia risk among nearly 360,000 military veterans.
Study author Deborah Barnes noted that many of the younger vets in the study had experienced concussions while in combat, often in Iraq and Afghanistan. Head blows among older vets were often due to falls or car accidents.
"Results were similar in the two groups," she said, "so we don't think there is anything special about these head injuries." That makes it more likely that the dementia risk seen among military personnel would also apply to the general population.
Barnes is a professor in the departments of psychiatry and epidemiology & biostatistics at the University of California, San Francisco's Weill Institute for Neurosciences. She is also a research health sciences specialist with the San Francisco VA Medical Center.
Roughly 179,000 of the study participants had been diagnosed with a traumatic brain injury (TBI) between 2001 and 2014. Just over half the group (54 percent) had specifically experienced a concussion.
Over an average tracking period of roughly four years, dementia risk among the TBI group was stacked up against that of an equal number of vets who had not experienced a TBI. On average, participants were nearly 50 years of age at the study's launch. About 9 percent were women, and nearly three-quarters were white.
In the end, the team found that less than 3 percent of the non-TBI group went on to develop dementia, compared with just over 6 percent of the TBI group.
Digging deeper, the investigators found that those who had never lost consciousness at the time of their head injury still faced a 2.4 times greater long-term risk for dementia. That figure rose to 2.5 among those who had lost consciousness. And among those who had experienced a moderate-to-severe TBI injury, dementia risk rose nearly fourfold.
"However, it is important to remember that not everyone who experiences a head injury will develop dementia," Barnes stressed. Although risk was significantly higher among TBI patients, the absolute risk still remained relatively low, she said.
Additionally, the study did not prove that head injuries caused dementia and "head injury is [just] one of many risk factors for dementia," Barnes noted.
"Even if you have had a concussion, you might be able to reduce your risk through other activities, such as engaging in physical, mental and social activity, and eating a brain-healthy diet," she suggested.
The report was published online May 7 in JAMA Neurology.
Dr. Ramon Diaz-Arrastia is director of the traumatic brain injury clinical research initiative at the University of Pennsylvania Perelman School of Medicine in Philadelphia. He said the findings confirm previous suspicions "with a greater degree of certainty than was previously possible."
Even mild traumatic brain injuries "are not always trivial," he noted. "The evolving literature certainly suggests otherwise. And the mechanical energy impact on the head and the brain is the same whether it comes from a car accident or fall, or potentially a blast injury incurred in combat," so the findings would apply to the military and the public alike.
"Head injuries are also very common in the general civilian population," added Diaz-Arrastia, who co-authored an accompanying editorial. "Something like 25 to 30 percent of the general population has had a concussion at some point in their life, although that number goes even higher among military personnel."
As for how best to handle a head injury when it occurs, he advised taking quick precautionary action.
"I think someone who has experienced a blow to the head to the point where they either lose consciousness or experience confusion, amnesia, disorientation or headache, or anything like that, should of course go to an emergency room," said Diaz-Arrastia.
"Most of the time, nothing will need to be done. But a small fraction of the time even a seemingly mild injury can evolve into a bigger deal," he advised.
There's more on traumatic brain injury at the U.S. National Institute of Neurological Disorders and Stroke.
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