(Ivanhoe Newswire) -- A device used to measure nighttime blood pressure
may interfere with patients' sleep, thus affecting the accuracy of the test
results.
"Blood pressure (BP), measured during sleep correlates better with heart attacks
and strokes compared to blood pressure measured in the doctor's office," Rajiv
Agarwal, M.D. of Indiana University and Veterans Affairs Medical Center,
Indianapolis, was quoted as saying. "However, if blood pressure measurement
disturbs sleep, then it may weaken the relationship between 'sleeping BP' and
these cardiovascular events."
Using a wristwatch-like device called an actiwatch, Agarwal and colleagues
analyzed the results of 24-hour blood pressure monitoring in 103 patients with
kidney disease. The purpose of this ambulatory blood pressure monitor was to
assess variations in blood pressure from day to night. Blood pressure normally
"dips" at night, but when it doesn't, the cardiovascular risks of high blood
pressure are much greater.
"We were measuring activity, sleep and ambulatory BP for diagnosing masked
hypertension and found this interesting observation," explained Agarwal. The
lack of normal nighttime 'dip' in blood pressure was related to increased
activity level, because the blood pressure monitor was disturbing the patients'
sleep. On nights when patients were using the blood pressure monitor, they spent
an average of 90 minutes less time in bed. They also spent less time asleep and
slept less efficiently.
Patients who awoke during the night were ten times less likely to have the
normal nighttime 'dip.' "Nighttime blood pressure is lower, not because of the
time of the day, but because people are asleep," said Agarwal. "The ambulatory
monitoring technique can disturb sleep, and therefore raise the nighttime blood
pressure as an artifact. Thus sleep quality should be taken into account when
interpreting blood pressure during sleep."
SOURCE: Clinical Journal of the American Society of Nephrology (CJASN), December
17, 2009
