When your blood pressure is taken at the doctor’s office, it is good news when it’s normal. But a growing body of scientific evidence now shows that these readings may be giving you only part of the picture.
New finding: Studies have reported that about 10% to 20% of people who have normal blood pressure in a doctor’s office actually have elevated blood pressure when outside the doctor’s office—a condition known as masked hypertension.
Why this is important: Like traditional hypertension (140/90 mmHg or higher), masked hypertension increases risk for coronary artery disease and stroke. In fact, people with masked hypertension may face even more risk because they don’t know they have it—leaving them without a diagnosis or the necessary treatment.
What you need to know…
Many people have heard of white-coat hypertension, the surge in blood pressure that occurs at medical offices when otherwise healthy people see a doctor and get their pressure tested. The theory behind this is that blood pressure rises because you’re anxious about having it measured.
Masked hypertension poses a different challenge. Because there’s no evidence of high blood pressure at the doctor’s office, blood pressure can remain elevated and untreated if it is not checked at home in those who have this condition.
How then can you tell if you have masked hypertension and need to be treated? Should everyone check his/her blood pressure at home, even if it was normal at the doctor’s office?
Watching for the danger zone: If your office systolic (top number) blood pressure reading is less than 120, you’re not likely to develop hypertension in the near future, since studies show that few people in this range have elevated pressure at home.
But if it is in the 130s, particularly in people under the age of 60, it would be considered borderline hypertension (also called prehypertension) and needs to be followed—both at home and in the doctor’s office. Most masked hypertension is actually borderline hypertension, a warning sign that you may need to improve your diet, get more exercise, lose weight and reduce excessive sodium intake.
The risk: Research has found that patients with masked hypertension have more than twice the cardiovascular risk—including risk for heart attack and atherosclerosis—as patients with normal blood pressure. Meanwhile, a recent study presented at an annual meeting of the American Society of Hypertension found that the risk for cognitive dysfunction in people with untreated masked hypertension was twice as high as for those who had controlled hypertension.
Of course, everyone’s blood pressure does naturally vary, depending on age, activity levels, stress and other factors. That’s why doctors should take at least two or three office readings, during separate appointments, before diagnosing traditional hypertension.
For a more complete picture, your physician might ask you to also take home readings (see below for details) to better assess your blood pressure and check for masked hypertension.
If your systolic readings are in the 130s in the doctor’s office, talk to your doctor about at-home blood pressure monitoring.
The main options for home blood pressure testing are either ambulatory or self-monitoring. Ambulatory monitoring, in which you wear a blood pressure monitor for 24 hours, provides a more reliable picture of your blood pressure and is considered a better predictor of cardiovascular risk than office measurements.
Self-monitoring allows you to check your blood pressure over time. To get the most accurate readings when self-monitoring, be sure to follow these tips…
• Don’t check every day. I tell patients not to check their blood pressure every day. It can become an obsession that can even affect your blood pressure readings. Your doctor can guide you on how often to check, depending on your readings and overall health. People with severe hypertension (frequent systolic readings of 160 or higher) or who have recently changed medications and/or doses may need to check their pressure more often until it is stable.
• Use an arm cuff. It’s more reliable than a wrist or finger device. I recommend Omron automated blood pressure monitors, which hypertension specialists consider to be reliable. Depending on the device, the cost can range from about $50 to $110.
What to do: Put the cuff in place with the bottom of the cuff about one-half to one inch above the elbow crease, then sit and relax for five minutes.
Next, take three readings a minute or so apart to obtain your resting blood pressure. Because the first reading can be unreliable, I recommend averaging the other two. As long as your doctor has found that your blood pressure is about the same in both arms, you need to check only one arm.
• Test at different times of day. It will help you get a sense of what your usual blood pressure is. However, you don’t want to test immediately upon awakening. Blood pressure is commonly elevated when you first wake up, so wait a half-hour or so.
Also important: Keep a written or digital record of your readings, and share them with your doctor. If your systolic blood pressure average is 135 or higher, your doctor may want to begin treatment with medication…and should also talk to you about better diet and exercise habits.
