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Does
Head Injury Increase Risk of Alzheimer's Disease?
New Findings Support Public Health Measures
to Reduce Head Trauma |
By Laurie Barclay, MD WebMD Medical News
Reviewed by Dr. Jacqueline Brooks
Many patients with Alzheimer's disease have a head
injury years before they develop the characteristic
memory problems, and researchers have long suggested
a link between the two conditions. But could it be
just a coincidence? Or does head injury in some way
trigger changes leading to Alzheimer's disease, or
make it appear earlier?
A new study reported in the Oct. 24 issue of Neurology
is helping to solve these mysteries, as it shows that
head injuries in young men are associated with an
increased risk of Alzheimer's disease and other dementias
in late life, and the risk goes up when the injury
is more severe.
"This study adds a few more pieces to the puzzle
in trying to determine the true association between
head injury and Alzheimer's disease," study author
Brenda L. Plassman, PhD, director of the epidemiology
of dementia program at Duke University in Durham,
N.C., tells WebMD.
"There is controversy as to whether head injury
is a risk factor for Alzheimer's disease or dementia,"
Carol F. Lippa, MD, tells WebMD. Both conditions are
very common about 4 million Americans have Alzheimer's
disease, and about 2 million Americans each year have
a head injury. So by chance alone, there is likely
to be some overlap.
Earlier studies examining this question suffered from
inaccuracies related to patients with Alzheimer's
disease, or their family members, reporting their
own history of head injury. "Remembering events
that may have occurred 50 years earlier may be fraught
with errors," Plassman says, and it is even more
difficult when the patient has memory problems. Fewer
than 70% of subjects in this study remembered a head
injury that was documented in their medical records.
Or the opposite may happen a patient with Alzheimer's
disease or his family may be searching for an explanation
for the condition, and therefore may be more likely
to assume that there was an earlier head injury. Or,
"when the time frame is immediate and the head
injury mild, the injury probably just draws the family's
attention to the patient. They then note an early
dementia that was not noticed before," says Lippa,
a professor and chief of neurology and director of
the Memory Disorders Program at the MCPHahnemann University
in Philadelphia.
This study solved some of these problems by relying
on medical records rather than patient or family reports
to document head injury. By examining military records
of World War II veterans hospitalized during their
service for head injury, or for other conditions unrelated
to head injury, the researchers found, examined, and
did psychological testing on more than 500 veterans
with documented head injury, and on more than 1,200
without it.
Severity of head injury was determined from how long
the veteran passed out or had no memory of the injury,
with mild head injury being less than 30 minutes,
moderate between 30 minutes and 24 hours, and severe
being longer than 24 hours.
Risk of Alzheimer's disease or of other forms of dementia
was about twice as high in those with moderate head
injury, and about four times as high in those with
severe head injury. Mild head injury did not significantly
increase risk.
"Whether prevention or better treatment of head
injury could influence later development of Alzheimer's
disease is an interesting question," Myron F.
Weiner, MD, tells WebMD. He is a professor and vice
chairman for clinical services in psychiatry at the
University of Texas Southwestern Medical Center in
Dallas, and reviewed the study for WebMD.
While professional boxers tend to get "punch-drunk,"
developing memory problems related to repeated blows
to the head, this study showed that even a single
moderate or severe head injury increased risk of Alzheimer's
disease up to 40 to 50 years later.
"From a public health point of view, such findings
add weight to the need to prevent head injury,"
Anthony Jorm, PhD, Dsc, tells WebMD. Countries such
as Australia have laws restricting boxing and requiring
the use of seat belts in cars, and helmets on motorbikes
and bikes.
"These measures are justified by the suffering
and disability that head injury can produce short
term, but now we must add in the possibility of dementia
down the track," says Jorm, professor and deputy
director of the Centre for Mental Health Research
at Australian National University in Canberra. "If
you can avoid head injury, do it!" study coauthor
James R. Burke, MD, PhD, tells WebMD. "I wouldn't
stop my child from playing competitive sports, but
I would encourage them not to box."
"We're starting to get a handle on factors that
could be important in developing Alzheimer's disease,"
says Burke, an assistant professor of neurology at
Duke University Medical Center.
Once genetic and other risk factors are defined, the
goal will be to predict who is likely to get the disease,
and to try to prevent it before they get even mild,
early symptoms. Recent research suggests that some
relatively safe medications, including anti-inflammatory
such as ibuprofen, might prevent Alzheimer's disease,
but more rigorous studies are needed.
Rita R. Handrich, PhD
UT Austin EAP |
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