Why Your Arm Shape Affects Blood Pressure Readings
Why Your Arm Shape Affects Blood Pressure Readings
Source:Medscape, August 4, 2025
Summary –
1. Background
• Blood pressure (BP) measurement is key in diagnosing hypertension and guiding treatment.
• Even small errors (e.g., 5 mm Hg) can misclassify millions of people worldwide.
• The standard cuff method (Riva-Rocci-Korotkoff) has been used for over 100 years but depends on proper technique and fit.
2. Sex Differences
• Automated cuff BP readings tend to be lower in women than men at the same true (intra-arterial) BP.
• This may hide cardiovascular risk in women and lead to undertreatment.
3. Anatomical Factors
• People with big differences between the top and bottom arm circumference get less accurate readings.
• Women often have a poor cuff fit because most cuffs are cylindrical and may extend past the elbow.
4. Cuff Size Effect (NHANES study, 3,735 adults, avg. age 45, 49% women)
• Women: The larger the cuff, the greater the underestimation (up to −6.4 mm Hg with extra-large cuffs).
• Men: Underestimation occurred only with extra-large cuffs (−2.4 mm Hg).
• Arm shape, body size, and fat distribution influenced accuracy in both sexes.
5. Key Findings
• Larger cuffs reduce accuracy, especially in women.
• Agreement between automated and manual BP classifications drops as cuff size increases.
• Risk: Misclassification of hypertension → inappropriate treatment.
6. Bottom Line
• BP cuff choice matters.
• Women, especially with larger cuffs, are more likely to have their BP underestimated, potentially missing needed care.
• More research is needed to adjust technology and improve cuff design for different arm shapes.
