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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.
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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 Alzheimers 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 teams
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. |
