Alzheimer's, Dementia & Mental Health
Memory May Not Be First Thing to Go for Those
Heading for Alzheimer’s Disease
Some of the earliest signs of preclinical AD may
occur on tests of visuospatial and speeded psychomotor skills
Oct.
13, 2009 – Senior citizens having trouble piecing together a jigsaw
puzzle may be showing signs of early Alzheimer’s disease, a new study
says. Cognitive abilities other than memory, including visuospatial
skills needed to perceive relationships between objects, may decline
years prior to a clinical diagnosis in patients with AD, according to a
report in the October issue of Archives of Neurology, one of the
JAMA/Archives journals.
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Alzheimer's, Dementia & Mental Health |
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Visuospatial skills are related to visual
perception of spatial relationships among objects: the visuospatial
skills needed to complete a jigsaw puzzle (Answers.com)
"Recent studies have focused on identifying the
beginning of the transition from healthy aging to dementia," the authors
write as background information in the article. "As new interventions
become available, it will become important to identify the disease as
early as possible."
Loss of episodic memory - remembering events in
one's life that can be explicitly stated - is commonly linked to
Alzheimer's disease, but it is not the only aspect of cognition
(thinking, learning and memory) that is affected.
David K. Johnson, Ph.D., of the University of
Kansas, and colleagues assessed 444 individuals who did not have
dementia when they were enrolled in the study, between 1979 and 2006.
Upon enrolling, each participant underwent a clinical evaluation and a
psychometric assessment including tests of four cognitive factors:
global cognition, verbal memory, visuospatial skill and working memory.
Participants were then evaluated at least one additional time before
November 2007.
Over an average follow-up of 5.9 years, 134
individuals developed dementia and 310 did not; 44 with dementia died
and underwent brain autopsies that confirmed a diagnosis of Alzheimer's
disease.
Using data from the psychometric assessments, the
researchers constructed models to evaluate the decline in various
cognitive areas before individuals were diagnosed with dementia.
"A novel finding was that visuospatial abilities
demonstrated an inflection point [sudden change to a steeper slope of
decline] three years before clinical diagnosis," the authors write.
Declines in overall cognitive abilities followed in
the next year, whereas inflection points for verbal and working memory
were not seen until one year before clinical diagnosis. Similar results
occurred in only the subgroup of individuals with Alzheimer's disease
diagnosis confirmed by autopsy.
"There are several implications of this study," the
authors conclude.
"Some of the earliest signs of preclinical disease
may occur on tests of visuospatial and speeded psychomotor skills.
Furthermore, the greatest rate of preclinical decline may occur on
executive and attention tasks. These findings suggest that research into
early detection of cognitive disorders using only episodic memory tasks,
such as word lists or paragraph recall, may not be sensitive to either
all of the earliest manifestations of disease or the most rapidly
changing domain."
"In summary, converging longitudinal evidence
suggests that after a sharp departure from the relatively flat course of
normal aging there is a preclinical period in Alzheimer's disease with
insufficient cognitive decline to warrant clinical diagnosis using
conventional criteria but that can be seen with longitudinal data from
multiple domains of cognition and not just memory," they conclude.
Editor's Note: This study was supported by grants
from the National Institute on Aging, National Institutes of Health.
