WASHINGTON, May 7 (Xinhua) -- American researchers reported on Monday in the journal JAMA Neurology that dementia was a possible complication following concussion even if the patient did not lose consciousness.
Scientists from the University of California, San Francisco (UCSF) tracked more than one-third of a million American veterans, and found that the likelihood of dementia more than doubled following concussion.
After adjusting for age, sex, race, education and other health conditions, they found that concussion without loss of consciousness led to 2.36 times the risk for dementia.
According to the study, these risks were slightly elevated for those in the loss-of-consciousness bracket (2.51 times) and were nearly four times higher (3.77 times) for those with the more serious moderate-to-severe traumatic brain injury.
In the total of 357,558 participants, whose average age was 49, half had been diagnosed with traumatic brain injury, of which 54 percent had concussion. The study followed participants for an average of 4.2 years, and 91 percent were male and 72 percent were white.
"There are several mechanisms that may explain the association between traumatic brain injury and dementia," said the study's senior author Kristine Yaffe, professor with the UCSF departments of neurology, psychiatry, and epidemiology and biostatistics.
"There's something about trauma that may hasten the development of neurodegenerative conditions. One theory is that brain injury induces or accelerates the accumulation of abnormal proteins that lead to neuronal death associated with conditions like Alzheimer's disease," said Yaffe.
"It's also possible that trauma leaves the brain more vulnerable to other injuries or aging processes," said Yaffe, "but we need more work in this area."