Losing Sleep Over Blood Pressure Monitors
Reported December 29, 2009
(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