Duke University Medical Center

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New
study illustrates that nearly every family will be faced with the
challenges of caring for a family member with some form of memory
impairment. |
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More
than a third of people over age 70 have some form of memory loss,
according to a national study by a team of researchers at Duke
University Medical Center, the University of Michigan, the University
of Iowa, the University of Southern California and the RAND
Corporation. The group performed the first population-based study to
determine the number of people who have some form of cognitive
impairment, with and without dementia.
While
an estimated 3.4 million Americans have dementia, defined as a loss of
the ability to function independently, the researchers estimate that
another 5.4 million over age 70 have memory loss that disrupts their
regular routine but is not severe enough to affect their ability to
complete the activities of daily living (ADLs).
"These
findings illustrate that nearly every family will be faced with the
challenges of caring for a family member with some form of memory
impairment," said Brenda Plassman, Ph.D., associate research professor
of psychiatry at Duke and the study's lead author. "Among the people
aged 71-79, a sizeable number had cognitive impairment. This is an age
at which most people expect to have many productive years ahead."
The
frequency of memory loss without dementia increased with advancing age
and with fewer years of education—similar to the trends seen in
dementia.
Plassman
explained that throughout the course of the study, individuals with
cognitive impairment without dementia progressed to dementia at a rate
of about 12 percent per year. On average, the mortality rate for the
study group was 8 percent annually, but varied across the subtypes of
cognitive impairment without dementia. Said Plassman, “While the
overall rate of progression to dementia is in line with findings from
other studies, the surprising finding here is that some subtypes of
cognitive impairment without dementia progressed to dementia at much
higher rates, around 20 percent, within one year."
Chronic Illnesses Named as Cause
Nearly
a quarter of those with memory loss without dementia also had a chronic
medical condition, such as diabetes or heart disease, that appeared to
be the cause of the cognitive impairment. The researchers speculate
that this group is one of the most underdiagnosed subtypes of cognitive
impairment because doctors are likely focusing on the primary health
issue.
"Given
how common cognitive impairment without dementia is, physicians should
be alert to this problem as they evaluate and treat the patient for
other medical problems," said Robert B. Wallace, M.D., the study's
senior author from the University of Iowa. "This may have significant
ramifications because it means that patients may not be able to
accurately portray their symptoms and may not retain important
information about their treatment."
The data, published in the Annals of Internal Medicine,
is from the Aging, Demographics and Memory Study, which is part of the
larger Health and Retirement Study conducted by the University of
Michigan Institute for Social Research and funded by the National
Institute on Aging.
"As
the population ages and works longer, understanding the extent of
cognitive impairment in the older population is critically important,"
notes Richard Suzman, Ph.D., director of the NIA's Behavioral and
Social Research Program. "Research is now beginning to suggest that
interventions—such as controlling hypertension and diabetes or perhaps
cognitive training—might help maintain or improve mental abilities with
age. As such interventions are tested and widely applied, we should be
able to track their impact through this type of research."
"With
such a sizable number of Americans with some form of cognitive
impairment, many of whom will get dementia, it's imperative to increase
research funding that could lead to breakthroughs in Alzheimer's
diagnosis, prevention and treatment," said William Thies, Ph.D., vice
president of Medical and Scientific Relations for the Alzheimer's
Association.
Co-authors
on the study include Kenneth M. Langa, Gwenith C. Fisher, Steven C.
Heeringa, David R. Weir, Mary Beth Ofstedal, James R. Burke, Michael D.
Hurd, Guy C. Potter, Willard L. Rodgers, David C. Steffens, John
McArdle and Robert J. Willis.