A study led by researchers at Johns Hopkins University Medical Center suggests that common arm positions during blood pressure (BP) screening may significantly overestimate blood pressure measurements, potentially leading to misdiagnosis of hypertension.
This study was published on October 7 in the journal JAMA Internal Medicine. Researchers analyzed the effects of three different arm positions on blood pressure measurements: arm resting on a table, supported on the lap, and unsupported at the side of the body. The study found that when the arm was resting on the lap, systolic blood pressure (the upper limit of blood pressure readings) was overestimated by an average of nearly 4 mmHg, while when the arm was unsupported, systolic blood pressure was overestimated by nearly 7 mmHg.
The Importance of Arm Position in Blood Pressure Measurement
"Arm position has a significant impact on the accuracy of blood pressure measurements," said Dr. Tammy Brady, senior author of the study and associate director of clinical research in pediatrics at Johns Hopkins University School of Medicine. The study further emphasizes the necessity of following clinical guidelines, namely, ensuring the arm is firmly supported when measuring blood pressure, such as by placing it on a table or other stable surface.
According to the American Heart Association (AHA), nearly half of adults in the United States have hypertension, defined as a systolic blood pressure (upper limit) ≥ 130 mmHg or a diastolic blood pressure (lower limit) ≥ 80 mmHg. If hypertension is not effectively controlled, it significantly increases the risk of cardiovascular diseases such as stroke and heart attack. Because hypertension often has no obvious symptoms, early screening and frequent monitoring during routine physical examinations are crucial for hypertension management. In most cases, blood pressure levels can be effectively controlled through lifestyle modifications (such as weight loss, a healthy diet, and exercise) and medication.
Research Methods and Key Findings
The latest AHA clinical practice guidelines emphasize that accurate blood pressure measurement requires the following: selecting an appropriate blood pressure cuff size, ensuring back support, feet flat on the ground without crossing legs, and the arm resting on a table or desk with the midpoint of the cuff at the same level as the heart.
Despite these clear recommendations, researchers point out that many improper procedures still exist in clinical practice. For example, many patients sit on the examination bed without arm support, or have their arms supported by healthcare professionals or the patients themselves. In this study, researchers randomly recruited 133 adults aged 18 to 80 years between August 9, 2022, and June 1, 2023, of whom 78% were Black and 52% were women.
Participants were randomly assigned to six different test groups to test the effect of different arm positions on blood pressure measurement. All measurements were conducted in a quiet and private environment, and participants were asked to avoid talking to researchers or using mobile phones.
Studies have found that compared to standard desktop support, the clinically common measurement method of placing the arm on the leg or hanging it on one side of the body results in significantly higher blood pressure values. Specifically, when the arm is placed on the leg, the systolic blood pressure is 3.9 mmHg higher and the diastolic blood pressure is 4.0 mmHg higher than the standard measurement; when the arm is hanging without support, the systolic blood pressure is 6.5 mmHg higher and the diastolic blood pressure is 4.4 mmHg higher.
The Impact of Overestimating Blood Pressure and Clinical Recommendations
"If blood pressure is measured incorrectly, each measurement of systolic blood pressure will be 6.5 mmHg higher. This means a person's systolic blood pressure could increase from 123 mmHg to 130 mmHg, or from 133 mmHg to 140 mmHg-and anything above 140 mmHg is considered stage 2 hypertension," explained Sherry Liu, coordinator of epidemiological research at the Johns Hopkins Bloomberg School of Public Health and one of the study's authors.
Dr. Brady stated that the study's findings highlight the need for clinicians to pay closer attention to measurement standards, and that patients should proactively request to follow optimal measurement methods when measuring their blood pressure in a medical setting or at home.