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 While severe and even moderate brain injuries have long been linked
to an increased risk of dementia, research to date on the link
between milder brain injuries and cognitive decline has been mixed,
particularly for cases when patients didn't lose consciousness.
For the current study, researchers examined data on almost 358,000
veterans, about 90 percent male. Half of them were diagnosed with
brain injuries between 2001 and 2014, and half were a control group
of individuals who were similar to the injured veterans but without
a history of brain injury.
Overall, 10,835, or 6 percent, of the veterans with brain injuries
were diagnosed with dementia during the study, compared with 4,698,
or less than 3 percent, of those without past brain injuries.
Compared to veterans without brain injuries, participants with a
mild traumatic brain injury who didn't lose consciousness were 2.4
times more likely develop dementia, and when they had lost
consciousness, their odds of a dementia diagnosis were 2.5 times
higher. Moderate to severe brain injuries carried an almost
quadrupled dementia risk.
"This data suggests that there is a higher incidence of dementia
after a head injury of any severity," said Dr. Jack Tsao, a
neurology researcher at the University of Tennessee Health Science
Center and Memphis Veterans Affairs Medical Center.
"However, much remains unknown about risks for why these individuals
developed dementia," Tsao, who wasn't involved in the study, said by
email.
When they joined the study, participants were 49 years old on
average.
A dementia diagnosis typically occurred about 1.5 years sooner in
people with brain injuries than people without brain injuries, Dr.
Kristine Yaffe of the University of California, San Francisco, and
colleagues note in JAMA Neurology.
Head injuries were tied to an increased risk of dementia even after
accounting for medical and psychiatric conditions that might
independently make people more likely to experience cognitive
decline.
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However, the study wasn't a controlled experiment designed to prove
whether or how brain injuries cause or accelerate the development of
dementia. It's also possible that medical records used in the
analysis didn't reflect mild or early stages of dementia in some
participants, the authors note.
Veterans are also exposed to more brain injuries than other people,
both because of combat and training activities as well as a tendency
to participate in more sports and leisure activities that can lead
to head injuries, said Dr. Ramon Diaz-Arrastia, a neurology
researcher at the University of Pennsylvania in Philadelphia and
director of the Penn Clinical TBI Initiative.
"The severity of the mild TBIs and the number of mild TBIs that
veterans are exposed to is higher than in the general civilian
population," Diaz-Arrastia, author of an accompanying editorial,
said by email.
"It is not uncommon for military veterans to report 3, 5 or even 10
or more mild traumatic brain injury exposures," Diaz-Arrastia added.
"That is more than in civilian populations (at least those who do
not play contact sports professionally) and clearly the total number
of exposures matters."
For soldiers and civilians alike, getting proper treatment and
taking precautions to avoid multiple hits to the head are crucial,
Tsao said.
"There is unfortunately no way to minimize dementia risk after a
traumatic brain injury," Tsao said. "However, with a concussion or
mild TBI, rest - cognitive and physical - as well as avoiding
re-injury are keys to immediate clinical recovery."
SOURCE: https://bit.ly/2FXSf6y and https://bit.ly/2ruFE6w JAMA
Neurology, online May 7, 2018.
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