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Delirium
rapidly accelerates memory decline in
Alzheimer's patients
Acute state of confusion and disorientation
often complicates hospitalization
BOSTON – Delirium often develops in elderly
patients during hospitalization or serious
illness, and this acute state of confusion
and agitation has long been suspected of
having ties to Alzheimer's disease and other
dementias.
Now a study led by researchers at Beth
Israel Deaconess Medical Center (BIDMC) and
Hebrew Senior Life confirms that an episode
of delirium rapidly accelerates cognitive
decline and memory loss in Alzheimer's
patients.
The findings are reported in the May 5 issue
of the journal Neurology.
"The cognitive rate of decline was found to
be three times more rapid among those
Alzheimer's patients who had had an episode
of delirium than among those who did not
have such a setback," according to lead
author Tamara Fong, MD, a staff neurologist
at BIDMC and Assistant Scientist at the
Institute for Aging Research, Hebrew Senior
Life.
"In other words, the amount of decline you
might expect to see in an Alzheimer's
patient over the course of 18 months would
be accelerated to 12 months following an
episode of delirium."
Alzheimer's disease is an irreversible,
progress form of dementia that gradually
destroys a person's ability to carry out
even the simplest of tasks, and affects as
many as 4.5 million individuals in the U.S.
according to figures from the National
Institute on Aging.
There is currently no cure for Alzheimer's
disease.
Delirium, on the other hand, is a
potentially preventable condition, which
often develops following a medical
disturbance, surgery or infection and is
estimated to affect between 14 percent and
56 percent of all hospitalized elderly
patients.
The investigators performed a secondary
analysis of data gathered from 408 patients
examined between 1991 and 2006 at the
Massachusetts Alzheimer's Disease Research
Center (MADRC). Over this 15-year period,
MADRC staff conducted a number of memory
tests on patients.
Testing was done on at least three
occasions, separated by intervals of
approximately six months. Seventy-two of the
participants developed delirium during the
course of the study.
In their final analysis, the authors found
that among patients who developed delirium,
the average decline on cognitive tests was
2.5 points per year at the beginning of the
study; following an episode of delirium,
decline nearly doubled to 4.9 points per
year.
"Although each dementia patient declines at
his or her own individual rate, the results
of our study tell us that this rate can
increase three-fold following an episode of
delirium," says Fong.
"As
an example, suppose an Alzheimer's patient
begins with mild symptoms, such as
forgetting appointments or details of
conversations, but over a period of the next
18 months, loses the ability to identify
relatives, becomes lost while driving
familiar routes, or can no longer balance a
checkbook or manage financial transactions.
"This
same patient, were he or she to experience
an episode of delirium, might experience
this same rate of decline in only 12
months."
While further investigations are needed to
determine the mechanism behind this
turn-of-events, Fong explains that delirium
may, in fact, be a key link in a chain of
events that results in injury to brain
cells.
"Older patients may be at greater risk of
developing delirium – particularly in the
hospital setting – because they tend to have
less 'reserve' or ability to compensate in
settings of increased stress. Consequently,
infections, new medications and other
stressors put the patient at risk for
delirium."
All elderly patients, but particularly
patients who have already been diagnosed
with Alzheimer's disease, can benefit from a
number of preventive measures if they are
hospitalized, notes Fong.
"As much as possible, it's important to try
and orient the patient to his or her
surroundings [i.e. frequently remind the
patient that he or she is in the hospital],
to allow for as much uninterrupted sleep as
possible by not waking patients to take
vital signs or do blood draws at night, and
to get patients out of bed and walking as
soon as their medical condition allows,"
notes Fong.
Also, important, she adds, is to avoid use
of unnecessary medications.
"Twenty percent of all elderly patients who
develop delirium go on to experience
complications, whether it's a prolonged
hospital stay, a move to a rehabilitation
center or long-term care facility, or even
death," notes Fong.
"Our current study now shows that delirium
can also adversely impact the state of
cognitive decline in patients with
Alzheimer's disease. Because up to 40
percent of delirium episodes can be
prevented, taking steps to avoid delirium
could result in significant improvements."
###
This study was funded, in part, by grants
from the Massachusetts Alzheimer's Disease
Research Center, the National Institute on
Aging, and the Alzheimer's Association, and
the VA Rehabilitation Career Development
Award.
Study coauthors include BIDMC investigators
Edward Marcantonio and Sharon Inouye; Hebrew
Senior Life investigators Richard Jones, P.
Shi, J.L. Rudolph, F.M. Yang and Douglas
Kiely; and L. Yap of Massachusetts General
Hospital.
Beth Israel Deaconess Medical Center is a
patient care, teaching and research
affiliate of Harvard Medical School and
consistently ranks in the top four in
National Institutes of Health funding among
independent hospitals nationwide.
BIDMC is a clinical partner of the Joslin
Diabetes Center and a research partner of
the Dana-Farber/Harvard Cancer Center. BIDMC
is the official hospital of the Boston Red
Sox. For more information, visit
www.bidmc.org.
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