Study Finds Why Your Seated Blood Pressure Reading May Not Be Accurate—Experts Explain
A new study finds the traditional way of taking blood pressure may not give accurate results.
Researchers discovered that some people only had high blood pressure while lying down.
Doctors say that incorrect blood pressure readings can lead to over- or under-treatment.
For years, major medical associations have recommended taking your blood pressure in the same position—seated, with your feet on the ground. But new research suggests taking your blood pressure while lying down flat on your back, a.k.a. supine, might yield more accurate results.
The study, which was presented at the American Heart Association (AHA)’s Hypertension Scientific Sessions 2023, followed more than 11,000 American adults and found that those who had high blood pressure both while seated upright and while lying flat on their backs had a higher risk of heart disease, stroke, heart failure, or premature death compared to those without high blood pressure when they were seated upright and while lying down.
While this is not necessarily shocking, the researchers also found that adults who had high blood pressure while lying flat on their backs, but not while they were seated, had similar risks of heart attack, stroke, heart failure, or premature death as adults who had high blood pressure in both positions.
Adding to this, the researchers found that 16% of those in the study who didn’t have high blood pressure when they were seated had high blood pressure readings in a supine position (a.k.a. lying down).
This raises a lot of questions about the best way to take your blood pressure. So, should you consider taking yours while you lie down? Here’s the deal.
What is a high blood pressure reading?
Blood pressure is the measure of the pressure of blood pushing against the walls of your arteries, per the Centers for Disease Control and Prevention (CDC). Having high blood pressure raises your risk of developing health problems like heart disease, heart attack, and stroke.
High blood pressure is usually defined as having a reading of 130/80 mm Hg, per the AHA. However, the CDC points out that some healthcare providers diagnose patients with high blood pressure if it’s consistently 140/90 mm Hg, which was the previous cut-off for high blood pressure before it was lowered in 2017. (This study used the updated 130/80 metric.)
Why is accuracy important with blood pressure readings?
Your blood pressure varies throughout the day and depending on what you’re doing, which is why it’s often recommended that you track yours at home over time if you have a higher reading at a doctor’s office, says Thomas Boyden, M.D., medical director for preventive cardiology and cardiac rehabilitation at Corewell Health. “Blood pressure readings in a physician’s office as well as blood pressure readings at home are important in understanding how well-controlled an individual’s blood pressure is,” he says.
Blood pressure readings will often dictate steps your healthcare provider will take to treat you properly. If yours is incorrect, it could lead to “overtreatment,” Dr. Boyden says, which could then cause you to take medication you don’t need. On the flip side, having a reading that’s lower than what it should be may mean you’re not treated enough, which raises your risk of heart attack, stroke, heart failure, and more serious health issues, per Dr. Boyden.
If you’re being monitored for high blood pressure, doctors will often take more than one reading or encourage you to take several at home. “We typically suggest taking three blood pressure readings separated by two to three minutes and recording the last one,” Dr. Boyden says. But if you’re not being monitored for high blood pressure, you’ll often just get one reading taken at your doctor’s office and that’s it.
“If blood pressure is only measured while people are seated upright, cardiovascular disease risk may be missed if not measured also while they are lying supine on their backs,” lead study author Duc M. Giao, a researcher and a fourth-year M.D. student at Harvard Medical School in Boston, said in a statement.
Why might taking blood pressure readings lying down be more accurate?
Your autonomic nervous system regulates your blood pressure when you’re in different positions, but gravity may cause your blood to pool when you’re seated or upright, the study’s authors explained. Your body is also sometimes not able to regulate your blood pressure when you’re lying, seated, or standing, which can throw your numbers out of whack.
“Blood pressure can drop when we sit or stand up, as compared to lying down,” says Jennifer Wong, M.D., a board-certified cardiologist and medical director of Non-Invasive Cardiology at MemorialCare Heart and Vascular Institute at Orange Coast Medical Center in Fountain Valley, CA. “The study results suggest that if we only rely on the sitting up blood pressure we typically measure, we might miss the folks who have elevated resting blood pressure because there can be that drop when they’re seated and standing.”
People are usually relaxed when they’re lying down, given that it’s linked to sleeping and lounging, Dr. Wong points out, and that can give a good measure of what their blood pressure is like when it should be at its lowest. “It’s important to check for elevated blood pressure when we’re relaxed,” she adds.
Should you take your blood pressure lying down, too?
The AHA currently recommends taking your blood pressure while seated in a chair, with both feet on the floor, and there’s no indication that the organization plans to change those recommendations based on the results of this one study.
However, Dr. Wong says it’s not the worst idea to consider checking your blood pressure while you’re lying down if you have concerns. “If we’re worried about missing high blood pressure in a person who always has readings within range sitting up, I suggest that they check it when lying down to make sure they’re not missing high blood pressure,” she says.
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