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Healthy
older brains not significantly smaller than
younger brains, new imaging study shows
Previous samples might have unknowingly
included people with early brain disease
WASHINGTON -- The belief that healthy older brains are
substantially smaller than younger brains
may stem from studies that did not screen
out people whose undetected, slowly
developing brain disease was killing off
cells in key areas, according to new
research.
As a result, previous findings may have overestimated atrophy and
underestimated normal size for the older
brain.
The new study tested participants in Holland's long-term Maastricht
Aging Study who were free of neurological
problems such as dementia, Parkinson's
disease or stroke.
Once participants were deemed otherwise healthy, they took
neuropsychological tests, including a
screening test for dementia, at baseline and
every three years afterward for nine years.
According to the report in the September Neuropsychology,
published by the American Psychological
Association, participants were also given
MRI scans at Year 3 to measure seven
different parts of the brain, including the
memory-laden hippocampus, the areas around
it, and the frontal and cingulate areas of
the cognitively critical cortex.
After examining behavioral data collected from 1994 to 2005 (with
scans taken between 1997 and 1999 depending
on when people entered the study), the
researchers divided participants into two
groups: one group with 35 cognitively
healthy people who stayed free of dementia
(average starting age 69.1 years), and the
other group with 30 people who showed
substantial cognitive decline but were still
dementia-free (average starting age 69.2
years).
That cognitive decline was measured by drops of at least 30 percent
on two or more of six core tests of verbal
learning and fluency, recall, processing
speed, and complex information processing,
and/or drops of 3 or more points, or scores
of 24 or lower (raising suspicion for
cognitive impairment), on the Mini-Mental
State Examination screening tool for
dementia.
In contrast to the 35 people who stayed healthy, the 30 people who
declined cognitively over nine years showed
a significant effect for age in the
hippocampus and parahippocampal areas, and
in the frontal and cingulate cortices.
In short, among the people whose cognition got worse, older
participants had smaller brain areas than
younger participants.
Thus, the seeming age-related atrophy in gray matter more likely
reflected pathological changes in the brain
that underlie significant cognitive decline
than aging itself, the authors wrote.
As long as people stay cognitively healthy, the researchers believe
that the gray matter of areas supporting
cognition might not shrink much at all.
"If future longitudinal studies find similar results, our
conception of 'normal' brain aging may
become more optimistic," said lead author
Saartje Burgmans, who is due to receive her
PhD later this year.
The findings should caution scientists about drawing conclusions
from brain studies that don't screen
participants over time, using precise and
objective definitions, the authors added.
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