Low
blood pressure in elderly
increases risk of dementia
Jan.
14, 2004 - Diastolic blood pressure below 70 raises the risk of dementia
in the elderly, says a new study of people 75 or older. For each
10-point drop in pressure, the risk of dementia increases by 20 percent.
Low pressures were only linked to an increased risk of Alzheimer's type
dementia, not the type that occurs as a result of blocked blood vessels
in the brain.
Like the age-old
question involving the chicken and the egg, the role of low blood
pressure (or hypotension) as cause or consequence of dementia has long
been studied by scientists. While many studies have suggested that low
blood pressure is a consequence of dementia, recent findings by
researchers at the Albert Einstein College of Medicine of Yeshiva
University demonstrate that low blood pressure may, indeed, be a cause
of dementia as well. Their research was published in the December issue
of the journal, Neurology.
“In individuals
with persistently low blood pressure, there was increased risk for
dementia developing,” says Dr. Joe Verghese, assistant professor of
neurology at Einstein. “And those participants whose blood pressure
was lowered through treatment for high blood pressure also demonstrated
an increased risk for dementia.”
Dr. Verghese and his
colleagues at the Einstein Aging Study followed 406 elderly individuals
over age 75, who all were dementia-free at baseline, at 12-to 18-month
intervals. Over the 21 years that participants in the observational
study were tested, 122 developed dementia. Having a low diastolic blood
pressure was associated with a significantly increased risk of
developing dementia, especially Alzheimer’s disease, the most common
type of dementia in the elderly.
At enrollment, a
detailed medical history was taken, including notations of any
prescription or over-the-counter medication participants were using.
Participants underwent a physical examination as well, which also
included detailed blood pressure measurements and neuropsychological
tests. On subsequent, annual, follow-up visits, the participants had
detailed clinical and neuropsychological evaluations to determine the
presence of dementia.
“The direction of
the relationship between blood pressure and dementia in our older
participants is opposite of that which has been found in middle-aged
populations where high blood pressure, not low, increases the risk of
dementia,” notes Dr. Verghese. “This may be due in part to a
significant age effect.
“Aging is
accompanied by significant structural and functional cardiovascular
changes, leading to raised pulse pressure in the elderly,” he
explains. “The rise is a consequence of arterial stiffness. Therefore,
in the very elderly, higher pressures may be needed to maintain adequate
blood flow in the brain – and may explain why previous studies of
older populations, over age 75 have also reported low blood pressure as
a risk factor for developing dementia.”
Dr. Verghese also
addresses his team’s converse finding regarding the treatment of
hypertension. “In younger populations, treating high blood pressure
has been associated with reduced risk of dementia,” he says. “Our
findings suggest that overtreatment, or treatment that is too
aggressive, may contribute to the adverse effects we found in our
elderly participants. Few other studies have represented very old
individuals over age 75.
“Our findings also
suggest that treatment guidelines for addressing high blood pressure in
the elderly might help ameliorate the risk of dementia developing.”
With low blood
pressure both a cause and consequence of dementia, the question is:
“Can maintaining blood pressure at optimal levels reduce the risk of
dementia in elderly individuals?” It is a question that Dr. Verghese
and his colleagues plan to explore.
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