TUESDAY, March 16, 2004 (HealthDayNews) -- Home blood pressure monitoring may be better at predicting your risk of a heart attack or other cardiovascular problem than the readings you get at your doctor's office.
In a study appearing in the March 17 issue of the Journal of the American Medical Association, French researchers report that a 10-point increase in systolic blood pressure readings at home translated to a nearly 20 percent increased risk of a cardiovascular event, such as a heart attack or stroke. In comparison, no jump in risk was found for an increase in physician's office blood pressure readings.
"This study shows that home blood pressure monitoring is like a motion picture, giving us consistent views over time, rather than a single snapshot, like [doctor's] office blood pressure readings," says Dr. Frank McGeorge, director of emergency medicine at William Beaumont Hospital in Royal Oak, Mich.
He says blood pressure readings taken at a doctor's office or in the emergency room are often elevated because people are usually anxious in such settings. The phenomenon is so common it's been dubbed "white-coat hypertension."
About one in four adults in the United States have high blood pressure, according to the American Heart Association. Many are unaware they have hypertension because the disorder is usually without symptoms. Left untreated, it can lead to heart disease, stroke and kidney disease.
In the current study, researchers followed almost 5,000 people who had been diagnosed with high blood pressure for an average of three years. The average age of the study participants was 70, and nearly half were male.
At the start of the study, three different blood pressure readings were taken in the doctor's office. Then, over a four-day period of the participant's choosing, blood pressure was taken at least three times throughout the day for each day. Home measurements were taken in a sitting position after five minutes of rest.
The researchers then followed the volunteers for an average of three years, recording any deaths or illness from cardiovascular disease.
They found home blood pressure readings were significantly better at predicting the incidence of cardiovascular disease than doctor's office measurements were. For each 10 mm/Hg rise in systolic (the top number) blood pressure readings taken at home, there was a 17.2 percent increase in the risk of cardiovascular disease. Cardiovascular risk went up nearly 12 percent for each 5 mm/Hg increase in diastolic pressure readings taken at home. Surprisingly, there was no similar association between increased blood pressure readings and cardiovascular risk when the readings were done at the doctor's office.
"Blood pressure readings don't correlate as well to risk as readings taken at home," McGeorge says. "The at-home reading is more likely to be true blood pressure. High blood pressure at home is a more significant finding."
Dr. Dan Fisher, a cardiologist at New York University Medical Center, says, "Home readings can give you a better assessment of continual blood pressure." But he adds the study had some limitations.
He says the volunteers' physicians were made aware of the home blood pressure readings, which may have influenced how they treated them. For instance, they may have treated people with elevated home readings more aggressively, he says. Also, the researchers didn't gather information on the type of treatment the study participants were receiving.
Both Fisher and McGeorge say home blood pressure monitoring is a good idea, particularly for people with hypertension. McGeorge also recommends it for anyone with known heart disease, or known risk factors for heart disease.
The most important thing, they say, is to make sure your home machine works well. Take it with you to your doctor's appointment, so you can compare your machine's reading to the doctor's reading to make sure your machine's readings are correct, they recommend.