It's a familiar ritual: Every time you go to the doctor's office, a nurse wraps a blood pressure cuff around your arm. You sit there quietly while the cuff inflates, and the nurse writes down your blood pressure.
But can you rely on that number? According to a statement released today by three major health organizations, maybe not. It turns out that measures you take at home, using a simple home monitor, may give a better idea of your risk for heart disease and stroke.
The new statement, released jointly by the American Heart Association, the American Society of Hypertension and the Preventive Cardiovascular Nurses Association, recommends that home blood pressure monitoring be used in most patients who have high blood pressure. The statement was created to help improve the treatment of high blood pressure, both in the United States and worldwide.
High blood pressure is "a major public health problem, and an important cause of heart attack, stroke, kidney failure and heart failure," said paper co-author Dr. David Goff, professor of public health sciences and internal medicine at Wake Forest University.
"In the U.S., only about a third of people with high blood pressure have it under control," he said. "Clearly, having people come to the doctor's office and have their blood pressure checked and treated isn't working."
No matter how good your nurse or doctor is, there's a difference between home blood pressure and blood pressure during a check-up. For one thing, if your doctor is listening through a stethoscope, outside noises can interfere. And the sounds he or she is listening for may be too soft to make out properly. Even electronic measurements can go awry at times.
Perhaps even more important, your body may be reacting to the stress of a doctor's appointment. As many as 20 percent of patients have something called "white coat hypertension." Some of these patients have high blood pressure only when they're in the doctor's office. At home, their blood pressure is normal. Without home monitoring, many of those people may wind up on blood pressure medicine that they don't need.
On the other hand, about 10 percent of people have lower blood pressure in the doctor's office than they do at home. These people may need to be on medication but their doctors won't know it if they just rely on office measurements.
There's good medical evidence to back all this up. Four out of five large studies of home blood pressure monitoring found that it was better than office measures for predicting problems like heart attacks or strokes.
Still, assuming you have "white coat hypertension" is no excuse for ignoring high blood pressure. Patsy McDermott, a family physician practicing in Malibu, Calif., has seen patients try to dismiss high numbers.
"A lot of times people will have high blood pressure in the office, and they say, 'It's only high when I come here.' However, there are all kinds of stressors throughout the day, not just trips to the doctor. To verify what's going on when you're not here, the home cuffs are good."
There are two main kinds of blood pressure monitor available: the traditional upper-arm style and the one that goes around your wrist. The wrist monitors are easy to use, and more and more people are buying them. They're also more likely to give inaccurate numbers, according to the American Heart Association, and aren't generally recommended.
"There are a lot of monitors out there, and some of them aren't very good," Goff said, warning that even upper-arm monitors could be inaccurate. "Patients should take their device to their doctor or nurse to make sure it agrees pretty well with the device being used in the office."
Dr. John D. Bisognano, a cardiologist at the University of Rochester Medical Center, agrees that wrist monitors can be problematic. "If the patient uses the monitors with great precision and reproducibility, they work okay," he said by e-mail. "But if not, the readings can vary widely and cause unnecessary alarm to the patient and provide inaccurate data. They may have some limited use in overweight patients who cannot obtain accurate readings using arm monitors, even with a large cuff."
Still, some patients are able to get good numbers from wrist monitors. A few of McDermott's patients are able to use them, although many others are not.
If your doctor recommends a home monitor, you can get one at the drugstore or online for about $75. You don't need a prescription.
Once you've got the proper kind of monitor, you need to use it correctly. It's tempting to take your blood pressure throughout the day, just to see how you're doing. Or, maybe your life is busy and you check your blood pressure when you remember. Neither of these methods gives you numbers your doctor can really use.
Eating, smoking, exercising and drinking coffee can all affect your numbers. To get the best readings, the heart association recommends checking first thing in the morning and again just before bed.
And they say to take more than one measurement each time, at least at first. To help your doctor diagnose high blood pressure — or make sure you don't have it — the recommendation is to check at least twice in the morning and twice before bed, every day for a week.
For patients, one of the most important things about home blood pressure monitoring may be that it puts you in control.
"There are examples of other chronic conditions where people are very involved in their own care," Wake Forest's Goff said.
And different kinds of home monitoring help people keep their illness under control.
"People with diabetes sometimes have to check their blood sugar four times a day," he said. "People with chronic heart failure have to weigh themselves daily. High blood pressure is another one of those conditions" for which patients could be more involved in their own care.
If you're monitoring your blood pressure at home, you can see the effects of a new medication, of improving your diet, of getting more exercise, or of cutting back on alcohol.
Family physician McDermott sees another potential advantage, too, just to having home monitors out there. "A good thing about it, and I've seen this happen too: hypertension is silent. And if you can measure your blood pressure, or a friend's blood pressure, and you can catch it, you can save a life."