Blood pressure is one of the most commonly measured signs of health. Almost everyone has had their blood pressure checked at a doctor’s office, pharmacy, hospital, or even at home.
These readings are important because high blood pressure, also called hypertension, is one of the leading causes of heart disease, stroke, kidney disease, and heart attacks.
The problem is that high blood pressure usually causes no obvious symptoms. Many people feel perfectly healthy even when their blood pressure is dangerously high. This is why accurate blood pressure measurements are so important.
However, a new study from researchers at the University of Cambridge suggests that the standard method used to measure blood pressure may not be as accurate as most people believe.
The findings, published in PNAS Nexus, may help explain why some cases of high blood pressure are missed and could eventually lead to better ways of measuring blood pressure in clinics and at home.
Studies have estimated that up to 30 percent of cases of hypertension may be missed because of inaccuracies in blood pressure measurements.
This means millions of people could be living with high blood pressure without knowing it. Without proper diagnosis and treatment, these individuals may remain at increased risk of serious health problems for many years.
The standard method for measuring blood pressure is called the auscultatory method. It involves placing an inflatable cuff around the upper arm and pumping it up until it temporarily stops blood flow through the artery. As the cuff slowly deflates, a healthcare professional listens with a stethoscope for a series of tapping sounds.
These sounds help determine two numbers. The first number is systolic blood pressure, which measures the pressure in the arteries when the heart contracts and pumps blood.
The second number is diastolic blood pressure, which measures the pressure when the heart relaxes between beats. A reading of 120 over 80 millimeters of mercury, written as 120/80 mmHg, is generally considered a healthy blood pressure.
Scientists have known for many years that cuff-based measurements have limitations. The standard method often underestimates systolic blood pressure and overestimates diastolic blood pressure.
Researchers already understood why the diastolic measurement can be inaccurate. However, they did not fully understand why systolic blood pressure readings often appear lower than they actually are.
To investigate this mystery, the Cambridge researchers developed a physical model that better mimics what happens inside real arteries during a blood pressure measurement.
Previous studies had used rubber tubes to imitate arteries, but these tubes did not behave like real human blood vessels. The Cambridge team instead used flat tubes that completely collapse under pressure, much like real arteries do.
The results were surprising. When the blood pressure cuff cuts off blood flow to the lower arm, the pressure below the cuff becomes extremely low. This low pressure keeps the artery closed for longer than expected as the cuff slowly deflates.
Because of this delay, the tapping sounds that indicate systolic blood pressure begin later than they should. As a result, the blood pressure reading appears lower than the person’s true systolic pressure.
This finding is important because systolic blood pressure is a major predictor of future heart disease and stroke risk, especially in older adults. If systolic blood pressure is consistently underestimated, some people who actually have hypertension may not receive the treatment and lifestyle advice they need.
The good news is that improving accuracy may not require expensive new equipment. The researchers suggest that simply raising the arm before taking a blood pressure reading may create a more predictable pressure below the cuff and improve measurement accuracy. This adjustment could potentially be introduced easily into everyday healthcare practice.
The findings could also help guide the development of future blood pressure devices. New devices may eventually be designed to account for factors such as age, body mass index, and differences in tissue characteristics that can affect blood pressure measurements. This could allow blood pressure readings to be tailored more precisely to each individual.
The research team hopes to conduct clinical trials to test these findings in real-world settings and determine whether the same effects occur in people of different ages, backgrounds, and health conditions. The study was funded by the Engineering and Physical Sciences Research Council, which is part of UK Research and Innovation.
This research serves as a reminder that even simple medical tests can have hidden limitations. Because high blood pressure often develops silently, accurate diagnosis is essential.
A few small improvements in how blood pressure is measured could help identify more people who need treatment and ultimately improve health outcomes around the world.
If you care about high blood pressure, please read studies that drinking tea could help lower blood pressure, and early time-restricted eating could help improve blood pressure.
For more health information, please see recent studies about added sugar in your diet linked to higher blood pressure, and results showing vitamin D could improve blood pressure in people with diabetes.
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