Blood pressure checks are one of the most common medical tests in the world. Almost everyone has had their blood pressure measured during a doctor’s visit, health screening, or hospital stay.
Doctors rely on these readings to decide whether a person is healthy or at risk for serious conditions such as heart disease, stroke, and kidney problems. However, new research suggests that the way blood pressure is usually measured may not always be as accurate as people believe.
Scientists from the University of Cambridge have discovered why the traditional arm cuff method can give incorrect results. Their findings may help doctors detect high blood pressure more accurately and prevent many cases from going unnoticed.
The study was published in the scientific journal PNAS Nexus, where researchers described how small changes in the measurement process could improve accuracy without needing expensive new equipment.
High blood pressure, also known as hypertension, is a major global health problem. It is considered the leading risk factor for early death worldwide because it damages blood vessels and puts strain on the heart over time.
Many people do not realize they have high blood pressure because it often causes no obvious symptoms. This is why accurate testing is so important. If high blood pressure is missed, patients may lose the chance to treat it early and prevent serious complications.
The most common way to measure blood pressure uses an inflatable cuff wrapped around the upper arm. The cuff is pumped full of air until it squeezes the artery and temporarily stops blood flow. As the air slowly leaks out, blood begins to flow again. A doctor or nurse listens with a stethoscope for tapping sounds that signal the return of blood flow.
These sounds help determine the two numbers in a blood pressure reading. The top number, called systolic pressure, shows the force when the heart beats. The bottom number, called diastolic pressure, shows the pressure when the heart relaxes between beats. A reading of 120 over 80 is considered normal for most adults.
This method, known as the auscultatory method, has been used for more than a century and is often called the gold standard. But researchers found that it may underestimate systolic pressure and overestimate diastolic pressure.
In other words, the test can make the top number appear lower and the bottom number appear higher than they really are. This could lead to some people with high systolic blood pressure being told their reading is normal.
To understand why this happens, the Cambridge team built a new model that better represents real human arteries. Earlier experiments used simple rubber tubes, but these did not behave like real blood vessels when squeezed by a cuff. The new model used materials that flatten and close in a way that closely mimics actual arteries inside the arm.
The scientists discovered that when the cuff squeezes the arm, it blocks blood flow to the lower part of the arm, creating very low pressure in that region. This low pressure keeps the artery closed longer than expected as the cuff deflates.
Because of this delay, the moment when blood starts flowing again is detected later than it should be. As a result, the systolic pressure appears lower than the true value.
This effect may explain why many people with high blood pressure remain undiagnosed. Some estimates suggest that up to 30 percent of people with hypertension may not be identified because of measurement errors.
Missing these cases can have serious consequences, since untreated high blood pressure increases the risk of heart attacks, strokes, and other life-threatening conditions.
The encouraging news is that the solution may be simple. Researchers believe that raising a patient’s arm before taking a reading could help balance the pressure differences and produce a more accurate result.
This small adjustment could be easily adopted in clinics and hospitals without new devices. Future blood pressure monitors might also include information about a person’s age, body shape, or tissue characteristics to further improve accuracy.
The Cambridge team now hopes to test their findings in real patients through clinical studies. They aim to work with healthcare providers to see whether these adjustments can improve diagnosis rates across different populations. If successful, the changes could help doctors detect high blood pressure earlier and start treatment sooner.
This research solves a long-standing mystery about blood pressure measurement and offers a practical way forward. More accurate readings could lead to better care, fewer missed diagnoses, and improved health outcomes for millions of people. As scientists continue to refine medical testing methods, even small improvements can make a life-saving difference.
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