Blood Pressure and the Brain

Hypertension is at the root of cognitive decline. It's becoming increasingly clear that high blood pressure, or hypertension, is at the root of much cognitive decline that has previously been attributed to aging. The more that scientists scrutinize brain function, and especially memory, the more they conclude that we have the ability to keep our memory and spirit strong well into old age.

By Willow Lawson, published on June 1, 2003 - last reviewed on August 18, 2005

The next time a nurse inflates a blood pressure cuff around your
bicep, pay attention. Those numbers are not just important for your
heart, but for your brain as well.

It's becoming increasingly clear that high blood pressure, or
hypertension, is at the root of much cognitive decline that has
previously been attributed to aging. The more that scientists scrutinize
brain function, and especially memory, the more they conclude that we
have the ability to keep our memory and spirit strong well into old age.
But it depends on how well we nourish our brain throughout life.

Hypertension is defined as blood pressure of 140/90 or above. The
first number is the measurement of the blood's force against artery walls
when the heart is beating. The second number is the pressure between
beats. A person is hypertensive if either number is too high.

Most people think salt is the culprit in high blood pressure. In
the vast majority of hypertensives, salt isn't the root of the problem.
Only about one third of people with high blood pressure are what doctors
call "salt sensitive."

"The rest of the folks can eat all the salt they want without
seeing much change in their blood pressure," says Shari Waldstein, Ph.D.,
associate professor of psychology at the University of Maryland at
Baltimore County, who studies the cognitive consequences of hypertension.
People whose diets are not to blame can pinpoint the problem through a
trial of medications that target differing pathways in the body. Blood
pressure is affected by many of the body's systems, including kidney
function, hormones such as insulin and the sympathetic and
parasympathetic nervous systems.

Regardless of cause, high blood pressure is extremely dangerous,
especially for people who don't know they have it, typically people who
rarely see a doctor. Hypertension has few symptoms; some sufferers
complain of headaches, nosebleeds or shortness of breath but for the most
part the body suffers in silence.

High blood pressure does its damage by weakening the blood vessels,
over time leading the inner lining to slough off. Vessels can be weakened
to the point that they tear, causing sudden death or disability via a
stroke or aneurysm. Hypertension can also lead to heart attacks.

But long before it creates a health emergency, hypertension takes a
subtle toll on mental faculties. It can reduce attention, learning,
memory and decision-making skills in ways that can be clearly seen in
studies.

"Generally, whatever problems impact cardiovascular health also
affect cognitive functioning," says Merrill Elias, Ph.D., a professor of
epidemiology at Boston University who has studied hypertension for 35
years.

Indeed, some researchers now believe that a substantial amount of
age-related mental decline has little to do with age and much to do with
blood pressure. Waldstein says there's a large body of research linking
hypertension directly to brain function, but scientists don't yet know
how it causes damage at the cellular level.

Elias says high blood pressure exerts a constant stress on the
brain and cardiovascular system that appears to be cumulative. "It's more
of a problem for people who don't go to the doctor," he says. "Just think
of it as your brain taking a hit every day."

The damage to the brain can come in a variety of forms. In the
elderly, more than half of whom suffer from hypertension, the damage can
be detected on MRIs in the form of "white matter lesions." These are
pinpoint lesions in the brain's message-carrying axons that affect
cognitive function, especially weakening memory and reasoning and
significantly impacting quality of life.

High blood pressure can also cause small strokes that may go
unnoticed, but which diminish the brain's capacity to function. Other
people who have chronic hypertension actually have small spots on their
brain where the tissue is dead, says Elias.

But that doesn't mean that high blood pressure is a disease of old
age. For one thing, many people who are in their 20s and 30s suffer from
it as well. It's especially important for younger people to control their
blood pressure so that the damage doesn't start early and snowball over
time.

But neither is high blood pressure inevitable with age. Blood
pressure can be kept in check by keeping cholesterol low, not smoking and
limiting salt. But perhaps the most important factor is keeping obesity
at bay, a struggle most Americans are not winning.

"Weight is a biggie," says Elias. "The more you weigh, the more
pressure there is."