I don’t think it’s as easy to accurately check your blood pressure as some think it is. And that’s a real problem.
Just because your blood pressure is high every time your doctor checks it in his office doesn’t mean that you have high blood pressure. There is just something about medical environments that raises the blood pressure in many people. It’s called white coat hypertension. And it’s very common.
So what doctors have come to rely on is what your blood pressures are when you are outside of the doctor’s office. For most people that is a much more accurate number. But what’s the best way to measure blood pressure?
I always ask my patients to rest quietly before they take their blood pressure in order to get the most accurate number. But now a new study is saying that this is the wrong way to check it.
So Who’s Right?
The authors of the study point out that for most doctors, home blood pressure measurement is the best way to diagnose and monitor high blood pressure. And just like me, most doctors emphasize a rest period before taking the measurement. But the authors questioned whether this is really the best way to check blood pressure.
So to find the answer, they enlisted a group of 52 men and women with high blood pressure. First, they had them check their blood pressure at home both after they had rested comfortably for a few minutes and also without any rest period.
Then the researchers fitted them with blood pressure monitors that they wore for 24 hours a day that checked their blood pressures every 15 minutes no matter whether they were resting, sleeping, or very active.
Finally, they compared the two methods.
When people took their blood pressures at home after a brief period of rest, their systolic numbers were lower than when they did it without the rest period. And they were also lower than the 24-hour blood pressure measurements.
The diastolic numbers did not seem to be affected either way. The authors of the study concluded that, “Rest before home blood pressure measurement induces a bias that underestimates systolic blood pressure.”
But I Completely Disagree With This Conclusion
Here’s why: First, the conclusion is based on the assumption that the 24-hour blood pressure monitor is more accurate than a simple resting measurement. But there’s no substantial data to back that assumption up.
The automated 24-hour measurements include measurements all during the day no matter whether the person was exercising, eating, sleeping, driving in rush hour traffic, or having a very tense moment. Are these situations in which an accurate blood pressure measurement can be determined? Not at all.
Blood pressure is a dynamic number. It goes up and down depending on whether the body needs it to be higher or lower. It’s not supposed to be the same in all situations. The danger in high blood pressure is not that it’s higher at any one given moment. The danger in high blood pressure is when it’s high all or most of the time – even at rest.
The other reason why trusting a resting blood pressure over a non-resting one is that for the most part, people are at rest. They spend an average of eight hours sleeping. And during the rest of the day, they have sedentary office-type jobs.
For both of these reasons, I believe that a resting blood pressure measurement is the most accurate method. So for me, the conclusion to this study should have been that not taking a rest period before checking your blood pressure will cause a bias that will overestimate the pressure – just like it does when you go to your doctor’s office.
Here Is How I Tell My Patients to Check Their Blood Pressure
(1) Buy an automated arm blood pressure monitor. If your arm is much larger than average, you will also need to buy an extra-large cuff. A cuff that is too small can give a falsely elevated reading.
(2) Before taking your measurement, be sure that you are seated quietly for at least a minute with your arm resting on a table at the level of your heart.
(3) Do it before you have any caffeine, and before exercise.
(4) After the first measurement, wait 15 seconds and take a second measurement. If they are essentially the same, record that reading. If they are different, measure your pressure a third time. Record the lowest reading as your blood pressure.
(5) Do this twice a day, usually before breakfast and again just before dinner, for about two weeks. Throw out any numbers that are unusually high or unusually low. These are called outliers and only represent isolated readings. Average the remaining numbers out, and that is your blood pressure. If that number is greater than 140/90, you should initiate some form of treatment. Refer to my website for ways to lower blood pressure without medication.
Boivin, J.M., E. Boutte, et al. “Home blood pressure monitoring: a few minutes of rest before measurement may not be appropriate.” Am J Hypertens. 2014 July;27(7):932-8.