Small Vessel Injury from Hypertension or Diabetes
May Lead to Dementia
One-third of risk for dementia attributed to small
vessel disease in autopsy study
April
9, 2008 – A large autopsy study of senior citizens who had lived in the
Seattle area has found that as many as one-third of those who had
dementia before they died also had small vessel damage in their brains –
the type of cumulative injury that can result from hypertension or
diabetes. The researchers say it suggests this accounts for a third of
the risk for dementia.
In the autopsied brains of people who had
experienced cognitive decline and dementia, 45 percent of the risk for
dementia was associated with pathologic changes of Alzheimer's disease.
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Alzheimer's, Dementia & Mental Health |
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Another 10 percent of dementia risk was associated
with Lewy bodies, neocortical structural changes that indicate a
degenerative brain disease known as Lewy Body Dementia. This is believed
by some clinicians to be a variant of Alzheimer's and/or Parkinson's
disease.
But a third of the risk for dementia (33 percent)
was associated with damage to the brain from small vessel disease.
Dr. Thomas Montine, University of Washington,
presented the study results at Experimental Biology 2008 in San Diego on
April 6. His presentation was part of the scientific program of the
American Society for Biochemistry and Molecular Biology (ASBMB).
Dr. Montine and his colleagues believe that this
small vessel damage is the cumulative effect of multiple small strokes
caused by hypertension and diabetes. These strokes are so small that the
person experiences no sensation or problems until the cumulative effect
reaches a tipping point. The researchers are now studying this small
vessel damage in more detail.
"This may be good news," says Dr. Montine.
"At a time when prevention and treatment for
Alzheimer's remain investigational, methods for preventing complications
of hypertension and diabetes are currently available.
"These findings are very different from both
conventional wisdom and from those of most autopsy studies of brain
aging and dementia."
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Memory, Cognitive Loss Decreasing in Older
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Why such different results? Perhaps because of the
broad reach of the population on which the autopsy study was based, says
Dr. Montine.
Most studies looking at the structural changes on
autopsy in brains of persons with dementia have focused on participants
in Alzheimer's disease center studies or in populations limited to one
gender, ethnic or professional group.
Individuals in this study were part of the Group
Health Cooperative, one of the oldest and largest managed care programs
in the United States.
Members in the group who reach age 65 with normal
cognitive ability are eligible to volunteer for an Adult Changes in
Thought (ACT) study, established by Dr. Eric Larson, director of
Research at the Group Health Cooperative. ACT participants undergo
cognitive, neurological and psychological tests every two years until
their death.
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Small Vessel Disease and
Strokes
Ischemic strokes can also be caused by stenosis,
or a narrowing of the artery due to the buildup of plaque (a
mixture of fatty substances, including cholesterol and other
lipids) and blood clots along the artery wall. Stenosis can
occur in large arteries and small arteries and is therefore
called large vessel disease or small vessel disease,
respectively.
When a stroke occurs due to small vessel
disease, a very small infarction results, sometimes called a
lacunar infarction, from the French word "lacune" meaning "gap"
or "cavity."
The most common blood vessel disease that causes
stenosis is atherosclerosis. In atherosclerosis, deposits of
plaque build up along the inner walls of large and medium-sized
arteries, causing thickening, hardening, and loss of elasticity
of artery walls and decreased blood flow.
National Institute of Neurological Disorders and
Stroke –
Read More |
Between 1994 and 2006, the period covered by this
study, 3,400 men and women entered the ACT study. They were
representative of the Seattle urban and suburban area: white, Asian,
African American and Hispanic, with a range of educational and
professional levels.
During this 12-year period, some participants
suffered cognitive impairment and dementia, while others did not.
Roughly a third of all participants died, and autopsies were performed
on the 221 who had given permission for this to be done.
With 55 percent of the risk for dementia
attributable to Alzheimer's and Lewy Body Dementia, these findings
underscore the therapeutic imperative for developing new pharmacologic
and other means of preventing or delaying the onset of Alzheimer's and
Lewy Body disease, says Dr. Montine.
But the unexpected finding that a third of the risk
for dementia is related to small vessel disease also provides an
additional reason to control hypertension and diabetes: not only to
protect cardiovascular and renal health but also to protect the health
of the brain.
