Blood pressure is one of the most common measurements taken during a medical visit.
It shows how strongly blood pushes against the walls of the arteries as the heart pumps and rests, and high readings over time can damage the heart, brain, kidneys and blood vessels.
Most people have their blood pressure checked while sitting in a chair. But research suggests that measuring it while a person is lying flat may reveal hidden risks that a standard seated reading can miss.
The study was led by Duc M. Giao, then a medical student at Harvard Medical School. The findings were presented at the American Heart Association’s Hypertension Scientific Sessions 2023.
Researchers examined health information from more than 11,000 adults who had taken part in a long-running U.S. study of heart and blood vessel health. Participants had their blood pressure measured while sitting and while lying down.
Blood pressure can change when the body changes position because gravity affects how blood moves through the body. Normally, the nervous system and blood vessels make quick adjustments to keep blood pressure and blood flow stable.
The researchers defined high blood pressure as a top reading of at least 130 mm Hg or a bottom reading of at least 80 mm Hg. These numbers are known as systolic and diastolic blood pressure.
About 16% of participants who did not have high blood pressure while sitting had high blood pressure when lying down. This meant their usual seated measurement could have made their blood pressure appear normal.
The researchers then looked at what happened to participants over many years. People who had high blood pressure while lying down faced greater risks of serious heart and blood vessel problems, even when their seated blood pressure was not high.
They had a higher risk of coronary heart disease, heart failure and stroke. They were also more likely to die early or from heart-related causes compared with people whose blood pressure was normal in both positions.
Importantly, people with high blood pressure only while lying down appeared to face risks similar to those whose blood pressure was high both sitting and lying down. This suggests that the lying-down measurement may contain useful information about long-term health.
There may be several reasons for the finding. Blood pressure regulation is complex, and abnormal readings while lying down could reflect problems with the body’s ability to control blood flow when a person changes position.
Lying-down blood pressure may also be relevant because people spend many hours in a horizontal position while sleeping. Previous research has shown that blood pressure during nighttime can provide important information about heart and blood vessel risk.
However, the findings do not mean everyone should immediately change how they measure blood pressure at home. The research was observational, so it found an association but could not prove that high blood pressure while lying down directly caused the increased health risks.
The study also focused largely on middle-aged adults, and more research is needed to understand whether the same pattern applies to older people and other groups. Researchers will also need to determine whether adding lying-down measurements to routine medical care improves treatment or prevents heart problems.
Still, the study raises an interesting possibility: one seated blood pressure reading may not always provide the full picture. Measuring blood pressure in another position could someday help doctors identify people whose cardiovascular risk might otherwise remain hidden.
The research was presented at the American Heart Association’s Hypertension Scientific Sessions 2023. As a conference presentation, the findings were considered preliminary at the time and had not yet undergone the full peer-review process required for publication in a scientific journal.
If you care about high blood pressure, please read studies that early time-restricted eating could help improve blood pressure, and natural coconut sugar could help reduce blood pressure and artery stiffness.
For more health information, please see recent studies about How to eat your way to healthy blood pressure and results showing that Modified traditional Chinese cuisine can lower blood pressure.
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