Home Blood Pressure Testing: More Accurate Than In-Office Testing
Research has demonstrated that there is a clear relationship between ]]>hypertension]]> and cardiovascular risk. For example, some studies have found that for every 10 millimeters of mercury (mm Hg) increase in systolic (the top number) blood pressure, and for every 5 mm Hg increase in diastolic (the bottom number) blood pressure, the risk of death due to heart attack or stroke can increase by as much as 30% and 40%, respectively.
Traditionally, people with hypertension monitor their condition with periodic blood pressure checks during a doctor’s visit. However, blood pressure monitoring in a physician’s office has certain drawbacks. For instance, the conditions under which the test is given may vary from one visit to the next. Additionally, because tests given in a doctor’s office may not always be given by the same person, there is a certain amount of subjectivity involved in reading the results. In-office monitoring may also cause “white-coat” hypertension (hypertension in which the patient’s blood pressure is elevated by the stress of being in the doctor’s office). Conversely, it may also fail to identify patients who have “masked hypertension” (blood pressure that is only elevated away from the doctor’s office.)
As in-home blood pressure monitoring devices have become more accurate, less expensive, and easier to use, some experts have been advocating for in-home monitoring to replace in-office monitoring as the standard of care. But, can in-home monitoring predict potential cardiovascular events as well as in-office monitoring?
A study conducted by a group of researchers in France says it’s not only as good, it’s better. Their study, published in the March 17th, 2004 issue of the Journal of the American Medical Association found that in-home blood pressure monitoring was more reliable than in-office monitoring for predicting patients’ risk of cardiovascular events.
About the Study
The researchers enrolled 4939 participants, all approximately 70 years of age and being treated for hypertension (140/90 mm Hg or greater). Home and office blood pressures as well as cardiac risk factors (age, male sex, smoking, diabetes, history of heart disease, or kidney failure) were assessed for each of the participants at the beginning of the study (baseline). A traditional blood pressure cuff was used to measure in-office monitoring and a printer-equipped, semiautomatic, digitized device was used for in-home monitoring.
The researchers followed the participants for approximately three years. At the end of the study, they determined the number of patients who:
- died from a cardiovascular event
- had a non-fatal heart attack or stroke
- experienced a transient ischemic event (mini-stroke)
- had been hospitalized for chest pain or heart failure
- required an invasive procedure to restore blood flow to the heart (revascularization)
The researchers found that at baseline, 13.9% of the participants had their hypertension under control in both the office and at home. Another 13.3% had blood pressure that was elevated in the doctor’s office but not at home, 9.4% had blood pressure that was elevated at home, but not in the doctor’s office, and 63.4% had hypertension that was uncontrolled in either setting.
They also found that with in-home monitoring, for each 10 mm Hg increase in systolic blood pressure, the risk of a cardiovascular event increased by 17.2% and for each 5 mm Hg increase in diastolic blood pressure the risk of a cardiovascular event increased 11.7%. However, for in-office monitoring, these same increases did not result in a significant increase in the risk of a cardiovascular event, suggesting that in-home monitoring was a better predictor of cardiovascular complications.
How Does This Affect You?
The results of this study suggest that for a sizable number of elderly hypertensive patients, in-office and in-home blood pressure measurements do not agree. More importantly, it also suggests that information gained from in-home testing is a better gauge of a patients’ risk of poor cardiovascular health down the road. This makes sense given the fact that in-home measurements are more likely to reflect a patients’ actual day-to-day blood pressure.
However, the findings from this study are not likely to end the debate. Another recent study, published in the February 25, 2004 issue of the same journal found that while in-home blood pressure monitoring allowed participants to decrease the amount of medications they were taking and modestly lowered treatment costs, it also resulted in slightly worse blood pressure control, presumably leaving the participants at greater risk for cardiovascular events.
The authors of the study published in February contend that managing high blood pressure exclusively with in-home blood pressure monitoring is probably not a good idea. However, they suggest that it may be useful when used in conjunction with office measurement. The authors of this study appear to have reached a similar conclusion, that accurately monitoring and treating patients with hypertension, which includes identifying patients with both white-coat and masked hypertension, ought to include at least some in-home blood pressure monitoring.
American Heart Association
National Heart, Lung, and Blood Institute
Bobrie G, Chatellier G, Genes N, et al. Cardiovascular prognosis of “masked hypertension” detected by blood pressure self-measurement in elderly treated hypertensive patients. JAMA . 2004;291:1342-1349.
Staessen JA, Hond ED, Celis H, et al. Antihypertensive treatment based on blood pressure measurement at home or in the physician’s office: a randomized controlled trial. JAMA . 2004;291:955-964.
Last reviewed March 19, 2004 by ]]>Richard Glickman-Simon, MD]]>
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