Health professionals often rely upon blood pressure measurements taken in the clinic to diagnose hypertension. If a patient has a blood pressure (BP) reading greater than 130/80 in a doctor’s office, he could be labeled hypertensive. That’s thanks to new guidelines from cardiologists. Over 100 million people now fit that category. But what’s the most reliable predictor of heart attacks or death from hypertension: blood pressure measurements taken in the doctor’s office or at home over 24 hours?
The Spanish Study
The New England Journal of Medicine (April 19, 2018) published the results of a study that ran from 2004 to 2014. Almost 64,000 Spanish patients were recruited for this trial. They had their blood pressure measurements taken in clinics following standard protocols. They were also sent home with a portable (ambulatory) device that recorded blood pressure measurements every 20 minutes during the daytime and every 30 minutes during the night.
The investigators then tracked how many of these people died over the length of the trial. After a median follow-up of 4.7 years, a total of 3,808 patients died. Cardiovascular causes accounted for 1,295 deaths.
The question the authors sought to answer was:
What was the best predictor of death: blood pressure measurements taken in the doctor’s office or at home with a 24-hour recording device (ambulatory readings)?
Hypertension was defined in the clinic as systolic pressure readings greater than 140 and diastolic BP readings greater than 90. People with ambulatory blood pressure measurements at home that were greater than 130 systolic and 80 diastolic were labeled hypertensive.
Ambulatory Blood Pressure Measurements Win!
An editorial in the New England Journal of Medicine (April 19, 2018) that accompanied the research described the results this way:
“They observed that ambulatory blood-pressure measurements were a stronger predictor of all-cause and cardiovascular mortality than clinic blood-pressure values.”
Interestingly, some patients had normal blood pressure measurements in the clinics but elevated blood pressure at home. This group was categorized as having “masked hypertension.” That’s because high blood pressure wasn’t detected in the doctors’ offices. Such patients would normally have been labeled “normotensive” and not treated. They were at the highest risk of death.
People with white coat hypertension not taking blood pressure medications were at somewhat higher risk of death. Patients with white coat hypertension who were taking blood-pressure-lowering drugs were not at higher risk of dying compared to normotensive patients.
Doctors have been arguing for years about which number is a better predictor of bad outcomes: the upper systolic number or the lower diastolic number. In this large study:
“Systolic blood pressure was a better predictor of mortality than diastolic blood pressure.”
If Your Life Were A Book:
This impressive Spanish study of blood pressure measurements suggests that the gold standard strategy is no longer in the clinic. To verify that a person really has hypertension, a 24-hour ambulatory monitor is the preferred approach.
Keep in mind, though, that this study involved one clinic visit and one, 24-hour home monitoring machine. In our opinion, the office visit is like looking at one sentence in a large book and trying to make sense of it. The 24-hour ambulatory blood pressure measurements equal one page in that big book of life.
We think that a far more representative method for monitoring blood pressure over months and years would be to measure your BP at home, at work and under a variety of different conditions throughout the day. When you do this over a long period of time and keep track in a diary or spreadsheet, you will have a far more accurate and nuanced assessment of your actual blood pressure. You can take this information to your physician. She will be able to analyze your situation and recommend a treatment program if necessary.
The People’s Pharmacy Perspective:
One of the great challenges of getting accurate blood pressure measurements involves technique. We have been dismayed to observe many mistakes when it comes to this most basic procedure. Here is an article describing some of the most common errors and how to correct them:
What are the best blood pressure monitors to use at home?
Here is our most recent article on the value of home blood pressure monitoring and the devices that have good ratings.
One Reader Shares His Experience:
Steve in Maryland is an engaged patient. Here is his story:
“Thank you very much for this article. I have been measuring my BP at home for 5 years. I keep the readings on a spread sheet. I’m 65 years old and take 10 mg of lisinopril. During a recent visit to my primary care doctor my blood pressure was once again measured incorrectly. It always is, and my readings are always higher than at home.
“When my doctor visited with me for 5 minutes he pulled up my chart on his iPad and told me that we needed to do more about my BP as it was borderline the last three visits. I shared with him my concern about the conflict between his data and mine. Remember, I have been measuring mine for 5 years. My data includes all seasons, time of day and every other influence.
“He pointed to his iPad and said here are the numbers. They don’t lie. I said yes, but I think mine carry more importance as there is more data and a broader sample. He stood firm on his information and had no interest in what I had to say. The conversation ended.
“When I first entered his practice many years ago I told him I am actively involved in my care. If exercise and diet help, I do it. If herbs or supplements help, I take them. If no other option exists other than a pharmaceutical, I take it. So, I ask questions and make my own decisions about the path I will follow. I don’t think he appreciates my level of knowledge and involvement.
“I don’t think it’s just him. Our medical care system is weighted toward what I call ‘check box medicine’ and drugs. Check box means you show up, they go through a number of preprogrammed steps and out the door you go with a drug or follow-up appointment. We can thank insurance companies, lawyers, bureaucrats and many others.
“In my book, nothing will change unless we the people learn to be the most important part of our care.”
Share your own story about blood pressure measurements below in the comment section. You may find our Guide to Blood Pressure Treatment of value.