Both higher and lower blood pressure may adversely affect cognitive
performance among the elderly, although age, education level, alcohol
consumption, and use of antihypertensive medications may influence those
outcomes, according to a report from a long-term study of 847 elderly
"Increased awareness is needed that the brain is an early target
organ of both high and low blood pressure before stroke and dementia,"
Shari R. Waldstein, Ph.D., of the University of Maryland, Baltimore County,
and colleagues reported in the March issue of the journal
"Younger age, higher levels of education, use of antihypertensive
medications, and some alcohol use may protect against the neurobiological
consequences of high blood pressure," wrote the authors, all researchers
with the Baltimore Longitudinal Study of Aging, a prospective study begun by
the National Institute of Aging in 1958.
"Both high and low diastolic blood pressure were associated with
poorer performance on tests of executive function and confrontation naming
among less-educated persons; with tests of perceptuo-motor speed and
confrontation naming among individuals not medicated with antihypertensives;
and with executive function among older individuals."
The researchers analyzed data from volunteer subjects dating back to
January 1, 1986, and excluded those with dementia, cerebrovascular disease, or
renal failure at baseline. The overall study uses a continuous recruitment
process, so the number of individual visits varied; the average was 2.7 visits
each. About 70 percent of the subjects were seen twice, and 52 percent had
Standardized blood pressure measurements were taken at each visit, and
participants took standard neuropsychological tests. The Digits Forward and
Backward parts of the Wechsler Adult Intelligence Scale—Revised assessed
attention and working memory. The California Verbal Learning Test evaluated
verbal learning and memory, and the Benton Visual Retention Test measured
nonverbal memory. Attention, perceptuomotor speed, visuomotor scanning, and
mental flexibility were assessed by the Trail Making Test, Parts A and B,
while Letter Fluency and Category Fluency tests examined phonetic and semantic
association fluency. The Boston Naming Test evaluated word finding. Results of
these tests were plotted against curves of higher and lower diastolic and
systolic blood pressure.
Participants under age 60 with higher systolic blood pressure made more
errors on the Benton Visual Retention Test and did worse on the Boston Naming
Test than those with normal systolic pressure, but improved over time,
probably as a result of a practice effect, said Waldstein and colleagues.
Among subjects aged 80 or older at baseline, those with higher systolic blood
pressure produced declining scores on the same tests over time.
However, participants with lower education levels and either high or low
diastolic blood pressure performed worse on the Boston Naming Test than those
with a mid-range diastolic pressure, producing a U-shaped curve for the
results. Among less-educated subjects, the Trail Making B test produced
similar results, but scores were significantly worse for those with high
diastolic pressure, creating a J-shaped curve.
Younger participants taking the Letter Fluency Test performed better if
they had higher diastolic blood pressure. But among older persons, both high
and low diastolic blood pressure predicted worse scores, compared with those
with mid-range blood pressure. Nondrinkers with higher systolic blood pressure
made more errors on the Benton Visual Retention Test than those who consumed
Taking antihypertensive medications affected test results, too, wrote
Waldstein and colleagues. Persons not on drugs to lower blood pressure scored
more poorly on the Boston Naming Test at both high and low diastolic blood
pressure levels, while their medicated counterparts performed similarly
through all blood pressure ranges.
"Elderly persons may be most vulnerable to the cognitive consequences
of higher systolic blood pressure over time," the authors stated, based
on the longitudinal decline on tests of nonverbal memory and confrontation
Both high and low blood pressure has been associated with effects on
cognitive function, said hypertension expert Vasilios Papademetriou, M.D.,
D.Sc., a professor of medicine at Georgetown University and director of
hypertension and cardiovascular research at the Washington, D.C., Veterans
Affairs Medical Center, in an interview. Diastolic blood pressure decreases
with age, while systolic pressure rises as people get older. The reason is the
same, though: arteries stiffen as part of the aging process. This divergence
of systolic and diastolic pressure (called isolated systolic hypertension) is
typical of advancing age and increases risk to the brain in several ways.
High blood pressure may cause cognitive declines by means of white matter
disease, brain atrophy, small silent infarctions, atherosclerosis in cerebral
or cervicocerebral arteries, or reduced cerebral blood flow. Low blood
pressure may cause insufficient cerebral perfusion, with subsequent
neuropathology, or may be related to cardiovascular comorbidities that could
decrease cognitive function, suggested Waldstein and colleagues.
"It is possible that over time the cognitive and neurobiological
correlates of hypotension and hypertension may progress to mild cognitive
impairment and/or dementia," they wrote. "This study... highlights
the need to further understand factors that increase individuals'
vulnerability to the cognitive consequences of high or low blood
Until further research clarifies those relationships, clinicians should not
hesitate to treat hypertensive patients out of fear that lowering diastolic
blood pressure will induce cognitive dysfunction, Papademetriou noted.
"We have no information showing that lowering diastolic blood
pressure is associated with dementia," he told Psychiatric
News. "Systolic blood pressure is associated with increased risk of
stroke, and stroke is the strongest contributor to dementia and cognitive
decline. Numerous studies over the last four decades have shown that optimal
treatment of hypertension will prevent about 40 percent of strokes."
Current national guidelines for a hypertension diagnosis—greater than
140/90 mm Hg, or for patients with diabetes and chronic kidney disease,
greater than 130/80 mm Hg—and treatment are set out in the Seventh
Report of the Joint National Committee on Prevention, Detection, Evaluation,
and Treatment of High Blood Pressure (JNC 7), published by the National Heart,
Lung, and Blood Institute, posted at<www.nhlbi.nih.gov/guidelines/hypertension>.
"Nonlinear Relations of Blood Pressure to Cognitive
Function" by Waldstein and colleagues is posted at<http://hyper.ahajournals.org/cgi/content/abstract/45/3/374>.
A report by Papademetriou, "Blood Pressure Regulation and Cognitive
Function: A Review of the Literature," is posted at<www.geri.com/geriatrics/article/articleDetail.jsp?id=142621>.▪