Higher nocturnal blood pressures are associated with lower scores on tests of cognitive function
Higher levels of blood pressure at night?especially
loss of the normal nocturnal dip in blood pressure?are linked to
lower scores on tests of cognitive function, according to a presentation
at the annual meeting of the American Society of Nephrology.
The results add to previous studies suggesting
that information from 24-hour blood pressure monitoring is a better
indicator of the risks of organ damage caused by hypertension than
blood pressure readings performed in the doctor’s office.
Led by Gary L. Schwartz, MD, of the Mayo
Clinic College of Medicine in Rochester, Minnesota, the researchers
compared 24-hour blood pressure recordings with the results of standard
cognitive tests in 389 patients, most of whom had hypertension.
The patients wore an ambulatory blood pressure monitor, which measures
and records blood pressure over a 24-hour period while patients
carry out their usual daily activities, including sleep. Past research
has shown that one-time measurements of blood pressure in the doctor's
office don't fully capture the health risks associated with disturbances
of blood pressure.
Scores on the cognitive tests were significantly
lower for patients with higher nocturnal blood pressure levels.
This included tests of specific cognitive functions such as attention,
processing speed, and others.
Normally, blood pressure drops by about 10
to 20 percent when a person lies down at night, compared with daytime
levels. In the new study, patients who didn't have this normal night-time
dip in blood pressure also scored lower on the cognitive tests.
Cognitive scores were unrelated to the patient's daytime blood pressure
levels on 24-hour monitoring, or to their blood pressure levels
measured in the doctor's office.
Through the sustained effects of high blood
pressure over time, hypertension can damage virtually every organ
in the body?including the brain. High blood pressure has been linked
to reduced cognitive functioning, even in young adults. The average
age of the patients in the new study was 63 years.
The new results show that higher nocturnal
blood pressure is also related to reductions in specific areas of
cognitive functioning.
Dr. Schwartz said: "These studies suggest
that we may have to pay more attention to blood pressure levels
and patterns throughout the day and night in order to protect our
patients from the harmful effects of high blood pressure."
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