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 The U.S. study spanning 20 years found steeper mental decline at the
end of that period among people who started out with hypertension or
even slightly elevated blood pressure - so-called prehypertension -
in their 50s and 60s.
These new results strengthen a link experts already knew about, lead
author Dr. Rebecca F. Gottesman told Reuters Health. High blood
pressure has been tied to an increased risk of stroke and dementia
in other studies.
“Basically the amount of decline we see associated with hypertension
is pretty modest, but this amount is equivalent to being 2.7 years
older at the start compared to not having it,” noted Gottesman, from
the neurology department at Johns Hopkins University School of
Medicine in Baltimore, Maryland.
“Even having prehypertension, which often isn’t treated, was
associated with some cognitive decline,” Gottesman said.
She and her team used blood pressure and mental performance data
from the early 1990s for over 13,000 adults between ages 48 and 67
years old. More than 5,000 remained alive and available for more
testing between 2011 and 2013.
After the first round of mental tests and blood pressure readings in
1990-1992, the verbal, memory and math tests were administered two
more times, in 1996-1998 and in 2011-2013.
Researchers divided the participants into three groups. Those with a
reading of less than 120 millimeters of mercury (mm Hg) systolic and
80 mm Hg diastolic during the early-90s measurements were considered
to have normal blood pressure.
Those with blood pressure up to 139/89 mm Hg were considered to have
prehypertension. Anyone above that reading and those with a
prescription for antihypertensive medication were considered to have
high blood pressure.
People with hypertension at the start were twice as likely to have
died by 2011 than those without it, according to the results
published in JAMA Neurology.
For those still alive, having high blood pressure at the first round
of tests was associated with 6.5 percent greater decline in mental
performance at the last round of tests than was seen in people with
normal blood pressure.
For people with prehypertension, the rate of mental decline over the
same period was somewhere in between those with hypertension and
those with normal blood pressure.
The differences are not huge, Gottesman said, but being the
equivalent of 2.7 years older mentally means that Alzheimer’s
disease, if it comes, will come earlier, and for the population in
general that would be an important difference, she said.
Those with high blood pressure who took medication to treat it had
an intermediate level of mental decline, similar to those in the
prehypertension group.
“People don’t tend to know what their blood pressure is nor do they
take it seriously because it doesn’t cause symptoms,” Gottesman
said.
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“Middle age may be an ideal time window to intervene on blood
pressure as the brain has not yet received a long-term or chronic
pounding from blood pressure elevation which can set the stage for
irreversible brain changes that affect cognition,” said Dr. Philip
B. Gorelick of Michigan State University College of Human Medicine
in Grand Rapids.
Gorelick wrote an editorial accompanying the new study.
By age 40, people should be keeping track of their blood pressure,
and perhaps earlier if they have a family history of hypertension,
Gottesman said – though you don’t need to check your readings too
often or become obsessed with it.
“At least have an idea of where you are,” she said.
“Our data suggests the lower the better but we didn’t have many with
very low blood pressure,” she said. “I think in general aiming for
the healthy range below 120/80 is a good idea.”
People with hypertension are usually told to aim for less than
140/90 mm Hg, Gorelick told Reuters Health by email.
Just following a group of people for several years, as in this
study, cannot prove that having high blood pressure actually causes
mental decline, only that the two are associated somehow.
“The jury is still out somewhat on what the mechanisms are,”
Gottesman said. “Honestly probably multiple things are going on.”
Some researchers believe that high blood pressure directly leads to
Alzheimer’s disease, while others believe high blood pressure causes
‘silent strokes’ and other changes in the brain that raise dementia
risk, she said.
The study underscores that for people with hypertension in middle
age, taking medication and controlling blood pressure levels through
diet, exercise and reduced salt intake are important measures, she
said.
“One would expect and hope that good cardiovascular health practices
would lead to preservation of cognition,” Gorelick said.
SOURCE: http://bit.ly/1qNNqiU
JAMA Neurology, online August 4, 2014.
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