Oct. 8, 2024 – People who have been diagnosed with high blood pressure may want to check again. That’s because many commonly used arm positions for blood pressure checks can lead to inaccurately high readings, researchers say.
Blood pressure readings using the recommended position of resting an arm on a heart-height surface were, on average, up to 6.5 points lower compared to other commonly used positions, such as hand-supporting the arm over the lap or when the arm is unsupported and hanging at the person’s side.
The differences are enough to move people between blood pressure ranges that may result in being prescribed medication. The findings suggest that high blood pressure is often overdiagnosed.
Patients “must advocate for themselves in the clinical setting and when measuring their BP [blood pressure] at home,” said lead study author Tammy Brady, MD, PhD, of Johns Hopkins University School of Medicine, in a statement.
Published Monday in the journal JAMA Internal Medicine, the study included 133 people whose average age was 57 years old. The results were consistent when the researchers took into account other factors like obesity, age, and recent access to health care, as well as whether people truly had high blood pressure according to the reading taken from the recommended position.
Clinical guidelines call for blood pressure readings to be taken with an appropriately sized cuff placed around the arm, with the back supported and feet flat on the floor. Legs should be uncrossed, and the arm should be positioned at heart level with the arm supported on a desk or table.
The people in the study went through a simulation of arriving at a clinic visit, such as walking for a couple of minutes beforehand, using the restroom to empty the bladder, and undergoing a seated 5-minute rest period before the reading was taken.
When the arm was supported on the lap, systolic blood pressure (the top number) was overestimated by 3.9 points, and diastolic (the bottom number) was overestimated by 4.0 points. Readings taken on an unsupported arm at the side overestimated systolic by 6.5 points and diastolic by 4.4 points.
A healthy blood pressure is considered less than 120 over 80 (commonly written as 120/80). The systolic blood pressure shows the blood’s force during a heartbeat. The diastolic blood pressure shows the blood’s force between heartbeats, sometimes referred to as “at rest.” High blood pressure is typically diagnosed at a reading of 130/80 or higher.
The researchers undertook the study because there are many situations during which blood pressure is taken and there is no easy access to a heart-height tabletop for resting the arm. A common scenario is when a person is sitting on an exam table.
The American Heart Association says that nearly half of all U.S. adults have high blood pressure, and people are more likely to develop the problem around middle age or later in life as arteries stiffen and plaque builds up in them. High blood pressure has many contributing factors, including poor diet, being overweight, sedentary lifestyle, and stress. The condition puts people at increased risk for serious health problems that are among the top causes of death in the U.S., like having a heart attack or stroke, so there has been an increasing focus on diagnosis and treatment across health care settings.
