Why Your Blood Pressure Probably Isn't as High as Your Doctor Says

One simple change could drastically lower rates of hypertension in the United States. No, it's not proper diet and exercise (though that would definitely make a dent); it's measuring blood pressure properly. According to a new study published in Scientific Reports, patients need 25 minutes of rest to ensure an accurate blood pressure reading.

About one-third of all American adults have hypertension, defined as a resting blood pressure reading of 140/90 mmHg or higher. The condition costs the nation $48.6 billion each year.

Prestigious organizations like the American Heart Association, the European Society of Cardiology, and the European Society of Hypertension recommend allowing patients to rest at least three to five minutes before measuring blood pressure. However, researchers at the University of Rennes in France found that this isn't nearly long enough. Blood pressure quickly rises during activity, and takes time to deflate to baseline levels.

Professor of Vascular Medicine Guillaume Mahé and his team measured the blood pressure of 199 resting patients (average age 66, 59% men) each minute over eleven consecutive minutes. They found that only half of subjects reached a stabilized blood pressure after five minutes. Extrapolating from their data, they determined that at least 25 minutes of rest would be needed to ensure an accurate resting blood pressure reading for 90% of them. (Below: Subjects' resting systolic blood pressure over time.)

Obviously, allowing patients to rest twenty-five minutes before measuring blood pressure is impractical, especially considering the jam-packed schedules of most medical practitioners and the frenetic nature of everyday life. However, prescribing expensive hypertension medications to people who don't need them is equally insensible. According to Mahé's results, almost half of the study group would have been diagnosed with hypertension if permitted only three to five minutes of rest. He projects that the rate would've dropped to just 35% if subjects were permitted to rest fifteen minutes.

Extrapolating to a larger scale, Mahé and his co-authors estimate that nearly 700,000 patients in France may be misdiagnosed for hypertension. That number could be five times higher in the United States! Thus, the researchers propose a fix.

"In our opinion hypertension diagnosis should be performed in a dedicated place during a specific consultation. At the very least, a suspicion of hypertension in a patient should warrant a second measurement after a longer rest period than the current recommended 5 minutes."

Doctors, nurses, and other clinicians may want to take this suggestion under advisement. In the meantime, replication of the current study with more subjects from diverse populations is needed.

Source: Mahe et al. "A minimal resting time of 25 min is needed before measuring stabilized blood pressure in subjects addressed for vascular investigations." Scientific Reports 7, Article number: 12893 (2017) doi:10.1038/s41598-017-12775-9