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 While the overall numbers are relatively small, former members of
the military who had received a concussion at some point in their
lives were 56 percent more likely to develop Parkinson's than
veterans who had not been knocked out, who had not experienced an
altered state of consciousness or who had not had amnesia for as
long as 24 hours.
When the brain trauma was more severe, the risk was even higher.
"This is not the first study to show that even mild traumatic brain
injury increases the risk for Parkinson's disease. But we were able
to study every single veteran across the U.S. who had been diagnosed
at a Veterans Affairs hospital, so this is the highest level of
evidence we have so far that this association is real," lead author
Dr. Raquel Gardner of the San Francisco VA Medical Center told
Reuters Health.
The importance of the discovery goes beyond veterans, the research
team writes in the journal Neurology.
Each year roughly 42 million people worldwide experience a
concussion, also known as mild traumatic brain injury. Such injuries
are especially common among athletes, in the military and constitute
"a growing epidemic among the elderly," the authors note.
"While the participants had all served in the active military, many
if not most of the traumatic brain injuries had been acquired during
civilian life," senior study author Kristine Yaffe of the University
of California, San Francisco (UCSF) and the VA said in a news
release. "As such, we believe it has important implications for the
general population."
The findings mean that "we need to dig in and figure out what the
mechanisms are," Gardner said in a telephone interview.
The researchers could not tell from their database analyses whether
cases of Parkinson's disease related to head trauma are somehow
different from other cases of the disease. That's in part because
the cause of Parkinson's, which afflicts more than a million people
in North America, usually after age 60, remains a mystery.
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The 325,870 veterans included in the study, ranging in age from 31
to 65, were typically followed for 4.6 years but the head trauma
often occurred long before that, and it is not known if the brain
injury accelerated the process, said Gardner, who is also affiliated
with UCSF.
But she stressed that while the increased risk seems high - it was
83 percent higher for veterans who had experienced more serious head
injury - the actual number of cases is relatively small.
Only 1 in 212 veterans who had experienced a concussion was found to
have Parkinson's. The rate was 1 in 134 among people who reported a
more serious moderate-to-severe traumatic brain injury at some point
in their lives.
"Even in our study, the vast overwhelming majority of veterans with
a traumatic brain injury did not get Parkinson's," Gardner
emphasized. "The risk is just a little higher among those who had
TBI. It's not a huge number of people because Parkinson's doesn't
affect a huge number of people. That's why it took a big study like
this to undercover this association."
People who had experienced head injury tended to be diagnosed with
Parkinson's two years earlier than people whose brains had not been
injured, the study also found.
A recent tally by the Department of Defense (https://bit.ly/1BfUZbS)
estimated that nearly 380,000 people on active military duty have
been diagnosed with a traumatic brain injury in the past 18 years;
82 percent of those servicemen and women experienced a mild
concussion.
SOURCE: https://bit.ly/2HyMhhr Neurology, online April 18, 2018.
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