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Alzheimers Warning Signs Show Up Years Before
Diagnosis
Aug. 1, 2005 - By combing through dozens of
Alzheimer's disease (AD) studies, psychologists have gained a clear
picture of cognitive problems in people who will develop the
degenerative brain disease. The meta-analysis reveals that people can
show early warning signs across several cognitive domains years before
they are officially diagnosed, confirming that Alzheimer's causes
general deterioration and tends to follow a stable preclinical stage
with a sharp drop in function.
Researchers at the Karolinska Institute and
Stockholm Gerontology Research Center, affiliated also with the Max
Planck Institute for Human Development and the University of South
Florida, crunched the data from a decade's worth of studies: Published
reports that met stringent criteria had records on 1,207 people with
preclinical Alzheimer's (they later developed the disease) and 9,097
controls who stayed healthy.
Neuropsychologists are striving to understand the
preclinical stage for two reasons: On the theoretical level,
understanding the transition from normal aging to dementia is vital to
understanding how the disease evolves. On the clinical level, treatment
can work best when doctors can identify at-risk individuals as early as
possible.
The authors studied 47 peer-reviewed studies
published between January 1985 and February 2003. The year 1985 marked
the introduction of more systematic and reliable diagnostic criteria for
Alzheimer's. The findings appear in the July issue of Neuropsychology,
which is published by the American Psychological Association.
The analysis showed that no matter what kind of
study, people at the preclinical stage showed marked preclinical
deficits in global cognitive ability, episodic memory, perceptual speed,
and executive functioning; along with somewhat smaller deficits in
verbal ability, visuospatial skill, and attention. There was no
preclinical impairment in primary memory.
The generalized nature of the problem is
consistent, say the authors, with recent observations that multiple
brain structures and functions are affected long before the AD
diagnosis.
They remind readers that the deficits seen in
preclinical AD mirror quite closely those seen in normal aging, such as
impairments in episodic memory, executive functioning, and cognitive
speed. Still, says lead author Lars Bδckman, PhD, these problems are
exacerbated in those who will go on to be diagnosed with dementia.
He explains, "There are no clear qualitative
differences in patterns of cognitive impairment between the normal old
75-year old and the preclinical AD counterpart. Rather, we think of the
normal elderly person, the preclinical AD person, and the early clinical
AD patient as representing three instances on a continuum of cognitive
capabilities. This presents an obvious challenge for accurate early
diagnosis."
The data also supported the emerging consensus that
AD's preclinical period is characterized by an early onset followed by
relative stability until a few years before diagnosis, when functioning
plummets.
Bδckman and his colleagues endorse a multi-variable
approach to understanding the preclinical stage of AD because this
approach will help clinicians to more accurately predict the likelihood
of disease.
The study traced other interesting patterns. People
younger than 75 years at baseline were more impaired at the outset than
people older than 75 at baseline. Impairment was also greater for the
patients with shorter periods (fewer than three years) to diagnosis.
These findings suggest that preclinical impairment is greater when the
disease starts younger and progresses more quickly, due to more
widespread and severe brain lesions among younger cases.
About the study
Article: "Cognitive impairment in preclinical
Alzheimer's disease: A meta-analysis;" Lars Bδckman, PhD, Karolinska
Institute, Stockholm Gerontology Research Center and Max Planck
Institute for Human Development; Sari Jones, PhD, Anna-Karin Berger,
PhD, and Erika Jonsson Laukka. PhD, Karolinska Institute and Stockholm
Gerontology Research Center; Brent J. Small, PhD, University of South
Florida. Neuropsychology, Vol. 19, No. 4.
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 human welfare.
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