Masked Hypertension: A Hidden Blood Pressure Danger

M.A., Health Writer
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Blood pressure has not been my friend, always difficult to control. I get agitated when I know it's going to be taken at the doctor's office. I also know that when I get excited or stimulated, my blood pressure increases in other situations. I am not alone.

Previous estimates have put the prevalence of white-coat hypertension, blood pressure increases in the doctor's office, at 15 to 30 percent of all people with high blood pressure.

The theory about whether this is a condition to be reckoned with used to lean toward, "Don't worry. They're just anxious in the doctor's office," because some people really do get anxious. Taken to an extreme, that is called iatrophobia. But truthfully, many people think, as the cuff goes on, "Wow, I haven't checked my blood pressure in a long time," or "I was pretty upset at that guy on the freeway, and I really blew off some steam, so my numbers may be high." They and I don't want to register high numbers, of course.

There have been substantial clues in the literature for a while now that maybe white-coat hypertension isn't as innocent as once thought. A study in The New England Journal of Medicine shows that ambulatory blood pressure measurements — "real world" blood pressure, taken over a 24-hour period, asleep or awake — are a stronger predictor of all-cause and cardiovascular mortality than clinic blood pressure measurements. All-cause mortality or death is generally thought of as all deaths that occur in a population, no matter the cause.

That was then and this is now

"A hypertension diagnosis based exclusively on blood pressure readings in the clinic is no longer acceptable," said lead study author Jose R. Banegas, M.D., of the Department of Preventive Medicine and Public Health, Autonomous University of Madrid, in an email interview with HealthCentral. "Ambulatory blood pressure monitoring (ABPM) should be part of the evaluation and follow-up of most hypertensive patients. Where it is not available or affordable, home blood pressure monitoring would be an alternative."

Sometimes your cardiologist will request you wear an ABPM device as a diagnostic, and it will be provided to you. As far as do-it-yourself choices, HealthCentral looked at prices for ABPM devices and found most in the low thousands. Amazon does have a few devices priced below $200.00, and chances are, as demand increases, prices will decrease.

The American Heart Association (AHA) says please don't buy and use a wrist or finger monitor, because they're just not as accurate. For regular at-home monitoring on a designated time schedule, it recommends an automatic, cuff-style, bicep monitor.

Accuracy is all when measuring

It's time to get current with monitoring, says Dr. Banegas. "We still are measuring blood pressure as we did 100 years ago: performing a few measurements with a mercury, aneroid (no liquid used) or, more recently, with an automated device in the medical office. However, many more people should use an ABPM device, which measures the blood pressure every 20 to 30 minutes during the 24 hours of an ordinary day. This technique accurately measures the usual level of blood pressure because pressure varies a lot along the day."

This due diligence could be, quite simply, life-saving, he says. "Our study suggests that a more frequent use of 24-hour blood pressure measurement could improve the diagnosis and management of hypertension, which is the first cause of premature death and disability worldwide."

The Centers for Disease Control and Prevention say that approximately 75 million adults have high blood pressure, or one in three. The condition results in more than 1,100 deaths each day.

Findings and global health implications

Dr. Banegas explains that the study also shows that masked hypertension — normal pressure in the clinic, but elevated out of the office — almost triples the mortality risk and white-coat hypertension — pressure elevated in the office but normal outside the office — almost doubles it in comparison with subjects with normal pressure in- and out-of-office.

"For example, a 50-year-old person with masked uncontrolled hypertension, compared with a normotensive (having normal blood pressure) subject, has a mortality risk equivalent to being 14-years older," he says. "We propose that the ABPM advantages should be adequately explained to physicians, the patients, and policymakers, and that ABPM use should be extended towards universal health insurance coverage. This may improve the health of patients and the sustainability of the health system, due to a better diagnosis and treatment of hypertension."

Guidelines also recommend monitoring

As noted earlier, the study findings weren't entirely new but "they validate in an important way some of the things we knew about ABPM," said cardiologist Boris Arbit, M.D. of UCLA Health in Los Angeles. "In the clinic we have one number, but the other 99 percent of the day, the number may be something entirely different. Remember that the most recent 2017 guidelines for blood pressure from the American College of Cardiology emphasized the importance of measuring blood pressure outside the office."

The white-coat syndrome shouldn't be ignored, he agrees. "Due to emotional factors, if blood pressure rises due to stress while in the clinic, it's probably rising throughout the day as well. It's important to emphasize the utility of measuring blood pressure outside the clinic, and that taking regular measurements with a good device and with good technique is essential."

Not everyone needs to be measured around the clock, because people have a life, he says. "But it is important to measure several times a day or consistently every day."

Take your blood pressure correctly

The AHA reminds you that taking blood pressure correctly means that you should:

  • Be still.
  • Don't smoke, drink caffeine, or exercise 30 within minutes of taking the measurement.
  • Empty your bladder and rest for 5 minutes first.
  • Sit correctly, back straight, feet flat, and legs uncrossed.
  • Support your arm on a flat surface.
  • Measure blood pressure at the same time every day.
  • Take two or three readings one minute apart and record them in a log manually, or use readings in your device's memory.
  • Take readings over bare skin, not clothing.

Always talk to your doctor about any blood pressure concerns, and do follow through if your doctor asks you to monitor yours.

See more helpful articles:

7-Step Plan for Managing High Blood Pressure

Can You Use Potassium to Lower Blood Pressure?

Salt Sensitivity: The Surprising Danger to Your Heart

Should I Start a Blood Pressure Log?