These white matter hyperintensities are often caused by silent strokes.
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Damage to tiny blood vessels in the brain might be a secondary
contributor to Alzheimer's disease, a new, small study suggests.
Areas of this blood vessel damage, called white matter
hyperintensities, are found in the brains of patients with Alzheimer's
disease and appear to raise the risk for the condition, the researchers
report. It is believed that the accumulation of beta amyloid plaques in
the brain are a primary factor in the development of the memory-robbing
condition.
"If you have both these white matter hyperintensities and amyloid in
the brain, then you are more likely to get Alzheimer's disease down the
road than if you just have one of these," said study senior author Adam
Brickman, an assistant professor of neuropsychology at Columbia
University's Taub Institute for Research on Alzheimer's Disease and the
Aging Brain.
The exact connection between this vessel damage and Alzheimer's
disease isn't exactly clear, he added. While the study showed an
association between the two, it did not prove a cause-and-effect
relationship.
"There are a number of things that happen through aging that can
influence the vessels of the brain, but there also might be an
interaction with Alzheimer's disease itself, where the disease is
damaging the vessels or the vessel damage is causing the Alzheimer's
disease," Brickman explained.
These tiny vessels might also become damaged through a variety of
conditions, including high blood pressure, low blood pressure, oxidative
stress, diabetes or inflammation, he explained.
The goal of the research is to one day target these damaged vessels
as a way to slow or prevent Alzheimer's disease, Brickman said.
"Maybe not a primary target, but certainly a potential target," he
said. "If we know what the risk factors for white matter disease are,
they are perfectly reasonable targets for either prevention or possible
treatment."
Limiting the damage to the brain's blood vessels is also important,
Brickman said. Keeping body weight and blood pressure levels in the
normal range and not smoking can go a long way in preventing Alzheimer's
disease, he said.
For the study, Brickman's team looked for blood vessel damage in the
brains of 20 patients diagnosed with Alzheimer's disease and in 21
people without the condition.
The researchers found that people with Alzheimer's disease had larger
areas of damage than those who were not diagnosed with Alzheimer's.
In addition, blood vessel damage in 59 people with mild memory
problems who were included in the study were signs that they were at
risk for Alzheimer's disease, the researchers added.
Brickman noted that these areas of blood vessel damage are seen in
most patients with Alzheimer's disease. "I think the reason we don't see
it in every patient is because the MRI technology we use might not be
sensitive enough to pick up all the changes in white matter disease," he
said.
The report was published in the Feb. 18 online edition of JAMA Neurology.
One expert said the damage to the tiny blood vessels is yet another
aspect to the development of Alzheimer's disease, but it complicates
understanding the condition.
"This study provides clear evidence that dementia patients in the
real world are more complex than those with the pristine pure
Alzheimer's disease that we select in research centers," said Dr. Sam
Gandy, associate director of the Mount Sinai Alzheimer's Disease
Research Center in New York City.
The causes of this blood vessel damage in the brain aren't well
understood, but it appears that these white matter hyperintensities do
signal brain damage linked to dementia, he said.
Gandy also noted these areas of blood vessel damage make it harder to
evaluate the effectiveness of drugs being tested to reduce plaque in
Alzheimer's patients.
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