Plate Nº 34 · recorded October 10, 2026
Health & Medicine ResearchReported finding
Letting Your Arm Hang During a Blood Pressure Check Can Add 6.5 mmHg
Johns Hopkins researchers found that letting your arm hang during a blood pressure check raised systolic readings by 6.5 mmHg—enough to push some patients into a stage 2 hypertension diagnosis.
By Elena Vasquez4 min read718 words
In brief
- Letting the arm hang unsupported at the side added 6.5 mmHg to systolic blood pressure readings on average
- Resting the arm in the lap added 3.9 mmHg to systolic readings and 4.0 mmHg to diastolic readings
- The study enrolled 133 adults (78% Black, 52% female) aged 18–80 between Aug. 9, 2022 and June 1, 2023
- Both unsupported positions can shift a borderline reading into stage 2 hypertension, defined as systolic pressure at or above 140 mmHg
- The findings appear in JAMA Internal Medicine, 2024, volume 184, issue 12, page 1436
An unsupported arm can add 6.5 mmHg to a systolic blood pressure reading—enough to move a borderline result into stage 2 hypertension, a Johns Hopkins Medicine-led study finds.
Researchers compared three arm positions in 133 adults. Resting the arm in the lap overestimated the top number—systolic pressure, the force when the heart pumps—by 3.9 mmHg. Letting the arm hang at the side pushed that figure up by 6.5 mmHg. Both habits show up often in routine clinic checks.
The study, published in JAMA Internal Medicine, examined how arm position changes readings clinicians use to diagnose high blood pressure. The American Heart Association puts the average target near 120/80 mmHg and estimates that nearly half of U.S. adults sit above that threshold.
What did the researchers actually test?
The team enrolled 133 adults—78 percent Black, 52 percent female, aged 18 to 80—between Aug. 9, 2022, and June 1, 2023. Each participant wore a cuff matched to their upper arm. A digital device collected three sets of three readings, 30 seconds apart, in each of three seated arm positions:
- arm supported on a desk or table
- arm resting in the lap
- arm hanging unsupported at the side
Before each measurement, participants emptied their bladders, walked for two minutes, and rested seated for five minutes with backs and feet supported. Researchers collected every reading in a quiet, private room and told participants not to talk or use phones during the tests.
How big is the difference?
Here is what each position produced compared with the desk-supported arm:
- Lap support: +3.9 mmHg systolic, +4.0 mmHg diastolic
- Unsupported at side: +6.5 mmHg systolic, +4.4 mmHg diastolic
- Reference: arm on a desk
Diastolic pressure—the bottom number, which reflects pressure in the arteries between heartbeats—rose as well.
"If you are consistently measuring blood pressure with an unsupported arm, and that gives you an overestimated BP of 6.5 mmHg, that's a potential difference between a systolic BP of 123 and 130, or 133 and 140 — which is considered stage 2 hypertension," said Sherry Liu, M.H.S., an epidemiology research coordinator at the Johns Hopkins Bloomberg School of Public Health and a study author.
Why does arm position change the number?
When the arm hangs or rests low, the cuff sits below the level of the heart. The hydrostatic pressure in the blood column between the heart and the cuff distorts the reading. The American Heart Association's clinical guidelines call for the cuff to sit at heart level, with the arm firmly supported on a flat surface, feet flat on the floor and legs uncrossed.
Yet the researchers say clinicians often skip those steps. Patients frequently sit on an exam table with no arm support, hold the arm in their lap, or have a clinician hold it for them.
What are the limits of this study?
The investigators flag two main caveats. All readings came from automated upper-arm devices; manual cuffs may behave differently. The participant group skewed toward older adults and included more Black adults than the U.S. average, so broader patterns across populations still need confirmation.
Senior author Tammy Brady, M.D., Ph.D., vice chair for clinical research in pediatrics at Johns Hopkins, says the results still show that arm position makes a "huge difference." Brady, who also directs the pediatric hypertension program at Johns Hopkins Children's Center, urged patients to push for proper technique.
"Patients must advocate for themselves in the clinical setting and when measuring their BP at home," Brady said.
What can patients do?
The Johns Hopkins team recommends three habits for anyone having blood pressure measured:
- Ask for the arm to rest on a desk or table, not in the lap or at the side.
- Make sure the cuff sits at heart level.
- Keep the back supported and feet flat, with legs uncrossed, for five minutes before the reading.
The work received funding from Resolve to Save Lives, backed by Bloomberg Philanthropies, the Bill and Melinda Gates Foundation, and the Chan Zuckerberg Initiative. Co-authors include Di Zhao, Ahmed Sabit, Chathurangi Pathiravasan, Junichi Ishigami, Jeanne Charleston, Edgar Miller III, Kunihiro Matsushita and Lawrence Appel. The journal reference is JAMA Internal Medicine, 2024; 184 (12): 1436.
via heart.org (Original)
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