Blood Pressure Measured Over Period Of Time Best

A Clearer Picture Needed For Physicians

Monitoring blood pressure at home can save money and give physicians valuable insight into a person's hypertension risk, according to a study reported in the Journal of the American Medical Association.

The researchers note that mixing readings at home and at the physician's office can spot true cases of high blood pressure.

"Don't base this treatment on one blood pressure reading in the office, because people are living the rest of the day -the other 23 hours and 45 minutes - and they've obviously still got a blood pressure," explains Dr. Dennis Goodman, chief of cardiology at Scripps Memorial Hospital in La Jolla, Calif.

"It's important to know the average blood pressure over time," Dr. Goodman says.

Looking at Home Blood Pressure Monitors

Sales of in-home portable blood pressure monitors have increased dramatically as patients play a greater role in their own health care. But few studies have examined whether self-monitoring actually saves money or improves patient care.

According to the American Heart Association, 50 million American adults now suffer from high blood pressure, a risk factor for heart attack and stroke.

A research team, led by Dr. Jan A. Staessen of the University of Leuven in Belgium, divided 400 hypertensive patients into two groups. Half of the patients received blood pressure readings during regularly scheduled visits to their physicians, while the other half measured their blood pressure on a daily basis at home.

One physician, treating without access to information on whether blood pressure readings were taken in the office or home, then made all decisions as to each patient's treatment over a six-month period.

According to the researchers, health-care costs for patients in the home-monitoring group were slightly lower - just under $5 per month less per patient on average when compared to those tested in physicians' offices.

Most of these savings were the result of home monitoring spotting patients with what is known as "white-coat hypertension."

"White-coat hypertension is the transient rise in a patient's blood pressure caused by stress in a medical environment, such as when his or her blood pressure is being measured by a doctor or nurse," Dr. Staessen explains.

In the absence of outside readings, white-coat hypertension can easily lead to a misdiagnosis of chronic high blood pressure.

Dr. Staessen estimates that about "30 percent of hypertensive patients have this condition."

Measuring blood pressure in the more relaxed environment of the home can produce lower readings and spare some patients misdiagnosis and unnecessary, expensive medication therapy.

Physicians and Patients Working Together

However, the study found that relying solely on home monitoring might not be a good idea, either. Patients in the home monitoring group had less long-term therapeutic control over their blood pressure than patients tested in the clinical environment, the researchers found.

Commenting on the study, Dr. Goodman says part of the problem is that what's "normal" in an office-based reading may not be normal at home, because of the influence of white-coat hypertension.

"All of these studies that we do that show a benefit with drug therapy are based on blood pressure measurements in the office," he says. "We really don't have studies based on what blood pressure is doing at home. So what is a normal blood pressure at home?"

Both Drs. Goodman and Staessen agree that more studies need to be done to help physicians make better treatment decisions.

The quality of many home-monitoring kits is questioned by some experts.

"The public is a victim to the lack of regulation in this field," Dr. Staessen says. "Most devices for blood pressure self-measurement are being sold without adequate instructions, [and] have not been properly validated according to current standards."

Dr. Goodman asks his patients to bring their monitors to his office for testing before he approves them for in-home use.

Dr Goodman says, "The first thing I do is tell them to go buy it, and tell the pharmacist or whoever you're buying it from that 'I'm taking this to my doctor, because I want him to verify that it's accurate. If not, I'm bringing it back.'"

Many of the devices prove inaccurate, especially those that measure blood pressure on either the finger or the wrist.

Dr. Goodman advises patients to stick to standard upper-arm monitors and to always take their pressure on the same arm in the same position each day.

Once he is satisfied with his patients' choice of monitor, Dr. Goodman will instruct them on its proper use and give them a personal schedule for taking at-home readings.

"What's so helpful about home monitoring is that patients get to see that it's not just what you're doing in the office, they can take it themselves," he says. "The more blood pressure readings you can get over the course of a day, the better."

Always consult your physician for more information. 

April 2004

Blood Pressure Measured Over Period Of Time Best

Looking at Home Blood Pressure Monitors

Physicians and Patients Working Together

What Is Blood Pressure?

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What Is Blood Pressure?

Blood pressure, measured with a blood pressure cuff and stethoscope by a nurse or other healthcare provider, is the force of the blood pushing against the artery walls.

Each time the heart beats, it pumps blood into the arteries, resulting in the highest blood pressure as the heart contracts.

One cannot take his own blood pressure unless an electronic blood pressure monitoring device is used. Electronic blood pressure monitors may also measure the heart rate, or pulse.

Two numbers are recorded when measuring blood pressure. The higher number, or systolic pressure, refers to the pressure inside the artery when the heart contracts and pumps blood through the body.

The lower number, or diastolic pressure, refers to the pressure inside the artery when the heart is at rest and is filling with blood.

Both the systolic and diastolic pressures are recorded as "mm Hg" (millimeters of mercury). This recording represents how high the mercury column is raised by the pressure of the blood.

High blood pressure, or hypertension, directly increases the risk of coronary heart disease (heart attack) and stroke (brain attack).

With high blood pressure, the arteries may have an increased resistance against the flow of blood, causing the heart to pump harder to circulate the blood.

According to the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH), high blood pressure for adults is defined as:

140 mm Hg or greater systolic pressure

and

90 mm Hg or greater diastolic pressure

In an update of NHLBI guidelines for hypertension in 2003, a new blood pressure category was added called prehypertension:

120 mm Hg – 139 mm Hg systolic pressure

and

80 mm Hg – 89 mm Hg diastolic pressure

The new NHLBI guidelines now define normal blood pressure as follows:

Less than 120 mm Hg systolic pressure

and

Less than 80 mm Hg diastolic pressure

These numbers should be used as a guide only. A single elevated blood pressure measurement is not necessarily an indication of a problem.

Your physician will want to see multiple blood pressure measurements over several days or weeks before making a diagnosis of hypertension (high blood pressure) and initiating treatment.

A person who normally runs a lower-than-usual blood pressure may be considered hypertensive with lower blood pressure measurements than 140/90.

Always consult your physician for more information. 

Online Resources

American Heart Association

Centers for Disease Control and Prevention (CDC)

Healthfinder, US Department of Health and Human Services (HHS)

National Heart, Lung, and Blood Institute

National Institutes of Health (NIH)

National Library of Medicine