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Older People With the "Alzheimer's Gene" Find It
Harder to "Remember to Remember"
Jan. 24, 2005 - Carrying the higher-risk genotype
for Alzheimer’s disease appears to render even healthy senior citizens
subject to major problems with prospective memory, the ability to
remember what to do in the future. For the group studied, this could
affect important behaviors such as remembering to take medicine at a
certain time or getting to a doctor’s appointment.
People with this genotype have a certain variety,
or allele, of a gene called ApoE (for Apolipoprotein E), which switches
on production of a protein that helps carry cholesterol in the blood.
ApoE has three alleles and about one out of five people carry the e-4
allele.
It makes homozygous carriers, who carry this
variation on both of their ApoE genes, eight times as likely to develop
Alzheimer’s disease as non-carriers. Heterozygous carriers, who carry
the high-risk variation only on half the pair, have a three-fold higher
risk. Neuro- psychologists have looked at the episodic, or
retrospective, memory, of e-4 carriers, especially for recent events.
This study was the first to look at their prospective memory.
At the University of New Mexico, a group of 32
healthy, dementia-free adults between ages of 60 and 87 were drawn from
a larger study of aging and divided evenly between people with and
people without the e-4 allele.
On a task in which participants were asked to
remember to write a certain word when they saw a target word, the
carriers showed significantly worse prospective memories. Far more often
than non-carriers, they failed to remember to write down the desired
word when they were supposed to – in other words, they forgot to do what
they meant to do, when they meant to do it.
Because the Alzheimer’s genotype had a strong and
obvious effect on prospective memory, the study’s authors recommend
changing the prevailing view that the allele has only subtle, often
undetectable effects on cognition. The findings also supplement previous
discoveries of how the allele also is linked to problems in episodic
retrospective memory, even without any signs of dementia.
Given these findings, clinicians can help even
healthy e-4 carriers to improve their prospective memory. Having been
found to be an important “exception to the rule” about the impact of
this genetic variation, prospective memory appears to merit more
research.
What’s more, co-author Mark McDaniel, PhD, says
that “Our results might provide some encouragement to the use of
prospective memory as an early diagnostic tool” because other research
has found a steep prospective-memory drop in patients with very mild
disease. He explains, “Our sample of carriers were healthy as far as we
could tell, but our assessments were not as sensitive as some of those
used at the major Alzheimer’s research centers. It might well be that
some of our carriers were in early AD stages that were not yet
detected.”
Replicating the results on a different group of
people, using ultra-sensitive tests, could result in the promise of a
simple test to aid in early diagnosis of Alzheimer’s disease.
Finally, McDaniel points out that major problems
with prospective memory could alert older adults to the presence of a
genetic risk for Alzheimer’s. He says, “It could be useful for someone
to recognize such a risk, as recent research suggests that lifestyle
factors such as diet, including cholesterol, may be important in the
development of the disease precisely for those with the genetic
predisposition.”
The research appears in the January issue of
Neuropsychology, which is published by the American Psychological
Association. The article is “Apolipoprotein E and prospective memory in
normally aging adults;” Ira Driscoll, PhD, and Mark A. McDaniel, PhD,
University of New Mexico, and Melissa J. Guynn, PhD, New Mexico State
University; Neuropsychology, Vol. 19, No. 1.
(Full text of the article is available from the APA
Public Affairs Office and at
http://www.apa.org/journals/releases/neu19128.pdf.)
Source: The American Psychological Association (APA),
in Washington, DC, is the largest scientific and professional
organization representing psychology in the United States and is the
world’s largest association of psychologists. APA’s membership includes
more than 150,000 researchers, educators, clinicians, consultants and
students. Through its divisions in 53 subfields of psychology and
affiliations with 60 state, territorial and Canadian provincial
associations, APA works to advance psychology as a science, as a
profession and as a means of promoting health, education and human
welfare.
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