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Silent vascular disease accompanies
cognitive decline in healthy aging
November 9, 2010— Older people who are leading
active, healthy lifestyles often have silent
vascular disease that can be seen on brain
scans that affect their ability to think,
according to a new study led by UC Davis
researchers and published online today in
of Neurology, one of the JAMA Archives
"This study shows that silent vascular disease
is really common as we get older and it
influences our thinking abilities," said
Charles DeCarli, professor of neurology in
the School of Medicine at UC Davis and
director of the UC Davis Alzheimer's Disease
"We're beginning to realize that vascular
disease plays a major role in Alzheimer's
disease — they go together."
The study findings are based on data from
participants in the Alzheimer's Disease
Neuroimaging Initiative. The initiative
tracks individuals who are normal, those who
have mild cognitive impairment (MCI) and
people with Alzheimer's disease using
magnetic resonance imaging (MRI), positron
emission tomography (PET) imaging and
laboratory and cognitive testing to track
changes in their cognitive status.
Over 5 million elderly people in the United
States have Alzheimer's disease, a
progressive, incurable and terminal disease
and the most common form of age-related
In its 2009 World Alzheimer Report, Alzheimer's
Disease International found that there are
more than 35 million people worldwide with
Alzheimer's disease or other types of
dementia. It also projected that the number
should nearly double in the next 20 years.
Cardiovascular disease, including hypertension,
high cholesterol and atherosclerosis, is
also common in the elderly, and causes
"white matter hyperintensities," regions of
damaged brain tissue that look like
white-hot areas on MRI scans. The purpose of
the study was to better understand the
relationship between white matter
hyperintensities and the extent to which
they precede, coincide with or follow
short-term changes in cognitive functioning.
For the study, more than 800 participants ages
55 to 90 were recruited from more than 50
research sites throughout the United States
and Canada. Some 200 participants were
cognitively normal individuals who were
followed for three years.
Approximately 400 people with mild cognitive
impairment also were followed for three
Two hundred people with Alzheimer's disease
were followed for two years. Potential
participants with serious brain anomalies,
such as brain tumors or prior surgery, were
excluded from the study.
All of the participants' baseline cognitive
functioning was established using clinical
diagnostic evaluation, including the Mini
Mental State Exam and the Alzheimer's
Disease Assessment Scale-Cognitive Subscale.
Criteria for the normal group included no
evidence of depression, mild cognitive
impairment or dementia. Individuals were
included in the MCI category if they had a
subjective memory complaint or objective
memory loss, among other measures.
Participants with Alzheimer's disease met
nationally accepted criteria for probable
Participants whose white matter
hyperintensities were significantly above
average at the beginning of the study lost
more points each year in cognitive testing
than those whose white matter
hyperintensities were average at baseline.
Those with mild cognitive impairment or
Alzheimer's disease at baseline had
additional declines on their cognitive
testing each year, meaning that the presence
of white matter hyperintensities and MCI or
Alzheimer's disease together added up to
even faster and steeper cognitive decline.
In addition, participants who were older at
baseline saw faster declines over time in
their Mini Mental State Exam scores.
The researchers found that, at the outset of
the study, the extent of white matter
hyperintensities was associated with greater
subsequent declines in global cognition over
a one-year period.
"In a sample … with frequent evaluations,
short-term follow-up and a relatively mild
profile of cardiovascular risk, white matter
disease may be an important predictor of
subsequent short-term global cognitive
change," the study found.
"There's a big group of people who have not had
major cardiovascular events such as heart
attacks. But we see signs that even milder
vascular-related insults can contribute to
loss of cognitive functioning," said Owen
Carmichael, the study's lead author and an
assistant professor in the Department of
Neurology in the School of Medicine at UC
Carmichael said that the study suggests that
reducing your cardiovascular risk factors to
a moderate level may not be enough to avert
all forms of brain disease that can lead to
cognitive decline in aging.
"Every little bit counts — you have got to
squeeze every little bit of healthy
lifestyle out of your day" to avoid brain
aging, he said.