Blood pressure checks are a routine part of most doctor visits, but new research suggests that the most common way we measure it may be giving inaccurate results — and that could mean thousands of people are going undiagnosed.
Scientists from the University of Cambridge believe they’ve now found the reason why, and their solution could be surprisingly simple.
High blood pressure, or hypertension, is one of the leading causes of early death worldwide. It’s strongly linked to heart disease, strokes, and heart attacks. Detecting it early is essential because high blood pressure often shows no symptoms until serious damage has already been done.
Yet according to researchers, the current cuff-based method — the one you’ve likely experienced at a clinic or pharmacy — can miss as many as 30% of cases of high systolic blood pressure.
The cuff-based method, officially called the auscultatory method, works like this: A nurse or doctor wraps an inflatable cuff around your upper arm, pumps it up until it stops blood from flowing to your lower arm, and then slowly releases the pressure.
As the cuff deflates, they listen through a stethoscope for specific tapping sounds, which reveal your systolic (top number) and diastolic (bottom number) pressures. Ideally, a reading around 120/80 is considered healthy.
Doctors have long known that these readings can be off — they tend to slightly overestimate the diastolic number and underestimate the systolic number — but no one has been able to explain exactly why the systolic reading is often too low.
Previous studies tried to recreate the process using rubber tubes to simulate arteries, but those models didn’t behave quite like real blood vessels and missed an important detail.
The Cambridge team decided to take a different approach. They built a physical model that closely mimicked what happens inside your arm during a blood pressure test, especially what occurs below the cuff when it’s inflated.
They discovered that when the cuff squeezes the arm and stops blood from flowing, the pressure in the lower arm (downstream pressure) drops very low.
This low downstream pressure keeps the artery clamped shut for longer as the cuff deflates. The result? The cuff “thinks” your blood pressure is lower than it actually is, which delays the moment it records your true systolic value.
This mechanism — the delayed reopening of the artery — is something earlier models failed to capture, but the Cambridge researchers believe it is the main reason for the underestimation. And since doctors aren’t currently adjusting for this, it means a significant portion of patients with high systolic blood pressure may be told their readings are normal.
The good news is that the fix might not require brand-new equipment. One idea the team suggests is as simple as slightly raising a patient’s arm before taking a reading. This could create a more predictable downstream pressure, making it easier to adjust the results.
More advanced solutions could involve future devices that collect extra information about a patient — like age, body mass index, or tissue characteristics — to fine-tune the readings for each individual.
The researchers now hope to test their findings in real clinical settings and work with doctors, engineers, and medical device companies to put these improvements into practice.
From a health perspective, the implications are huge. If this simple adjustment leads to more accurate readings, it could help identify many people with hidden high blood pressure who would otherwise go untreated. And in the fight against heart disease and stroke, catching the problem early can save lives.
If you care about blood pressure, please read studies that timing matters when taking high blood pressure pills and 1 in 5 people with high blood pressure taking a drug worsen the disease.
For more information about blood pressure, please read studies that new research challenges conventional blood pressure guidelines and scientists make a big breakthrough in high blood pressure treatment.
The study is published in PNAS Nexus.
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