The difference in blood pressure between arms linked to a greater risk of death, new study finds

By Sarah MooreReviewed by Emily Henderson, B.Sc.Dec 21 2020

A new study finds that a difference in blood pressure between arms is associated with an increased risk of heart attack, stroke, and death.

A team of researchers at the University of Exeter led the large-scale meta-analysis of all relevant research projects, combining data on over 54,000 people from a total of 24 studies conducted in Africa, Asia, Europe, and the US. Data collected on blood pressure readings taken from both arms were included.

In a paper published this month in the journal Hypertension, the team concludes that greater differences between the blood pressure of the arms are linked with an increased risk of death and illness.

Blood Pressure. Image Credit: kurhan/Shutterstock.com

Understanding the link between blood pressure and health implications

Scientists have long understood that differing blood pressure between the arms is associated with poorer health outcomes. However, until now, the full extent of the health implications had remained unclear.

Blood pressure readings are given as two numbers, as the upper limit of maximum blood pressure (systolic), and minimum level (diastolic). People who have high systolic blood pressure are considered to have hypertension, a health implication that affects around a third of adults and is known to increase the risk of heart attacks, strokes, and death.

Previous research has revealed that differences in systolic blood pressure between the arms are related to artery narrowing which can impact blood flow. These arterial changes are considered to be risk factors for cardiovascular events, including heart attack, stroke, and even death.

Reviewing international blood pressure guidelines

Researchers of the current project recognized the need to gain a deeper understanding of the relationship between differences in systolic blood pressure between the arms and these health implications.

To do this, the team analyzed data collected over a decade on inter-arm blood pressure difference, as well as heart attacks, strokes, and deaths. The study’s results revealed that each 1 mmHg difference in systolic blood pressure between the two arms translated to a 1% increase in predicted 10-year risk of new angina, a heart attack, or stroke.

Dr. Chris Clark, the study’s lead author, summarizes the significance of the results, “it tells us that the higher the difference in blood pressure between arms, the greater the cardiovascular risk, so it really is critical to measure both arms to establish which patients may be at significantly increased risk. Patients who require a blood pressure check should now expect that it's checked in both arms, at least once.”

Currently, it is the protocol to measure food pressure in both arms when assessing a patient’s cardiovascular risk, according to international blood pressure guidelines. However, these recommendations are often ignored, and blood pressure readings are often only taken from one arm. The findings of the new study emphasizer the importance of following this guidance.

Clark highlights the relative ease of following the guidelines, and the potential impact it could have, “checking one arm then the other with a routinely used blood pressure monitor is cheap and can be carried out in any healthcare setting, without the need for additional or expensive equipment. Whilst international guidelines currently recommend that this is done, it only happens around half of the time at best, usually due to time constraints."

Our research shows that the little extra time it takes to measure both arms could ultimately save lives”.

The study’s findings also suggest that the UK and European guidelines on blood pressure should be revised. Currently, guidelines state that a 15 mmHg systolic difference between the two arms is the threshold indicative of elevated cardiovascular risk.

However, the results of the new study demonstrate that this should be reduced to 10 mmHg. According to the new evidence, a 10 mmHg difference is the upper limit of what is normal, and anything greater may indicate an increased cardiovascular risk.