High Nighttime Blood Pressure May Mean Low Daytime Performance

Finding supports the use of 24-hour blood pressure monitoring, experts say

FRIDAY, Nov. 11, 2005 (HealthDay News) -- For some people, sluggishness during the day could be rooted in abnormally high blood pressure during sleep the night before, new research contends.

Researchers believe an absence of the normal nighttime dip in blood pressure may bring about what is considered a cognitive slowdown.

The finding also highlights the importance of ambulatory blood pressure monitoring, in which patients use a portable device that monitors their blood pressure continuously over a 24-hour period.

"It's not surprising, it makes sense, and I advocate that there should be more ambulatory modeling for identifying those patients at a high risk for high blood pressure," said study lead author Dr. Gary L. Schwartz, an associate professor of medicine at the Mayo Clinic College of Medicine in Rochester, Minn.

Experts have long known that the use of a small, portable monitor can pick up abnormal nighttime readings that would otherwise go unnoticed during a blood pressure test in the doctor's office.

The American Heart Association (AHA) estimates that one in three Americans has high blood pressure. Almost one-third of the 50 million affected men and women, however, remain unaware of it, because such symptoms as headaches, dizziness, and nosebleeds typically manifest only at the most advanced stages of the condition.

The study authors emphasized that this so-called "silent killer," if left unmonitored and uncontrolled, can injure every organ in the body and raise risks for stroke, heart attack, heart failure and/or kidney failure.

In their study, Schwartz and his colleagues provided 389 men and women, averaging 63 years of age, with ambulatory blood pressure monitors worn constantly over a 24-hour period.

After testing all the patients for basic cognitive abilities -- such as attentiveness and speed while executing tasks -- the researchers compared the results with both one-time office and ambulatory blood pressure readings.

In a report that was to be presented Friday at the American Society of Nephrology's annual meeting in Philadelphia, the authors said that those patients with the higher nighttime blood pressure scored lower on their cognitive tests.

Also, patients who did not experience the normal 10 percent to 20 percent dip in blood pressure levels while asleep also scored lower on their ability tests.

These nighttime "dips" below daytime blood pressure levels are normal for healthy patients.

The researchers noted that sluggish cognitive performance during the day was only associated with changes in nighttime pressure, not levels of daytime pressure as measured either by 24-hour monitoring or during a typical office visit.

Again, the finding pointed to an expanded role for 24-hour ambulatory readings when assessing a patient's blood pressure, the researchers said.

"The problem is that there's no one who pays for ambulatory readings, which is a very practical concern," stressed Schwartz. "Medicare will cover it under very restricted circumstances, but most third-party insurances will not, and patients will have to pay for this cost out of pocket. Hopefully, studies like this one will help to change the situation for the future."

Schwartz emphasized that while money is an issue, patient compliance is not.

"I really do think people are willing to undergo the 24-hour blood pressure test," he said. "They're quite lightweight, and patient acceptance is really quite high."

Hillel W. Cohen, an associate professor of epidemiology and public health at Albert Einstein College of Medicine in New York City, said the findings were "interesting" and agreed they could lead to increased use of 24-hour blood pressure monitoring.

"However, I think the 24-hour equipment is still cumbersome, and as the technology makes it easier to record this, it may become a more useful tool," he suggested. "It certainly gives a more precise estimation for BP risk. But the interpretation of the 24 [hour] BP is not so simple, and the ability to do it on everybody is limited, so I think it still remains as something for people who have already been identified for being at high risk."

More information

For more on monitoring high blood pressure, check out the National Heart, Lung, and Blood Institute.

SOURCES: Gary L. Schwartz, M.D., associate professor, medicine, Mayo Clinic College of Medicine, Rochester, Minn.; Hillel W. Cohen, DrPH., associate professor of epidemiology and public health, Albert Einstein College of Medicine, New York City; November 11th presentation, American Society of Nephrology meeting, Philadelphia.
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