I use a wearable continuous blood pressure monitor, a device likely to transform hypertension diagnosis and treatment.

My broker urged me to do the annual “Discovery Wellness Experience”, which offers “Diamond Status”, hence rewards – coffee! It didn’t feel like a Wellness Experience when the Discovery person reported my blood pressure (see below) as  143/81, which is high. I was sure a second measurement would be normal but surprised to see the repeat value – almost exactly the same. My Wellness level plummeted as I worried about joining the 1.3 billion people worldwide, and one third of adults in SA affected by hypertension (high blood pressure). Was this just a “white coat” effect? I resolved to find out.

The message in my Discovery app.

Prevention is better than cure, but screening and testing isn’t necessarily problem free. Tests have false positives, carry a cost, may result in unnecessary procedures, and can generate significant anxiety. I favour limited, evidence-based health “interventions”, like an annual flu shot (and Covid immunisations), and a colonoscopy every 10 years (not fun, but I have a family history). I control my “lifestyle” risks (non-smoker, regular exercise, minimal alcohol, healthy diet though high in dark chocolate) but I don’t take supplements and I don’t do annual “check-ups”, heart tests, etc.

Hypertension (high blood pressure) is a silent killer that’s often undiagnosed because symptoms typically are absent for years while the disease relentlessly damages the heart, brain, and kidneys. So your BP is worth checking at regular intervals – once a year over the age of 40, less frequently (every 2-5 years) before that, unless you have risk factors like a family history, black ethnicity or diabetes.

Even when diagnosed and treated, hypertension is often poorly controlled. This may be due partly to the limitations of traditional BP measurement methods. Wearable continuous blood pressure monitoring devices enable earlier intervention, more personalised treatment, and perhaps better long-term outcomes.

Traditional blood pressure monitoring

Blood pressure is measured using a sphygmomanometer. (In Greek, sphygmos is “pulse”, and manometer means “pressure meter”). The original sphygmomanometer (see below) was a manual device: the operator inflated the arm cuff by squeezing a rubber bulb then listened with a stethoscope over the artery at the elbow for characteristic sounds while the cuff gradually deflated. Today, apply the cuff correctly, and press a button. No rubber bulb, mercury column or stethoscope. Three or four numbers automatically appearing on a screen – the heart rate, the higher BP number (the systolic), and the lower number (the diastolic pressure). Clinic/hospital devices also display the mean (average) blood pressure.

But assessing BP with current automated devices, in the doctor’s office or at home, has limitations:

• Some patients have higher-than-normal BP in clinical settings due to anxiety (“white coat syndrome”) leading to overdiagnosis and unnecessary treatment.
• Others have the opposite – normal BP in the clinic, but raised blood pressure out in the world ( “masked hypertension”).
• Traditional BP monitoring provides only snapshot readings, which may not accurately represent an individual’s typical blood pressure through the day.
• Nocturnal hypertension (high blood pressure at night, when BP is normally lower) is a an important predictor of cardiovascular events, but goes undetected with standard measurement methods.
• Many patients struggle to measure their BP consistently and accurately, leading to incomplete or inadequate data for decision-making. BP should be measured after being at rest for 5 minutes, in a seated position, with a correctly sized cuff applied to the upper arm, and the legs uncrossed.

These challenges highlight the need for continuous, passive, accurate blood pressure monitoring. Wearable technology now makes this possible.

How wearable continuous BP monitors work

Advances in sensor technology, AI and machine learning, and miniaturisation have led to the development of wearable, non-invasive, continuous BP monitoring devices.

Cuffless devices use either photoplethysmography[1] (PPG) or pulse transit time (PTT)[2] to estimate blood pressure. AI algorithms calibrate these readings against traditional BP measurements.

Some wearables mimic traditional BP devices with integrated, wrist-worn inflatable cuffs. They provide regular intermittent readings but because of the periodic inflation, are less comfortable for 24-hour use.

These wearable BP monitors allow frequent, real-time tracking of blood pressure fluctuations in daily life, offering new insights.

Transforming hypertension diagnosis

Early detection of hypertension

Continuous BP monitoring could help identify hypertension at an earlier stage, especially in people with borderline high readings or high cardiovascular risk.

People with a family history of hypertension could be monitored passively over weeks or months, leading to early detection and timely intervention.

Many people experience high BP at night, which is associated with a much higher risk of stroke and heart failure. For the first time, wearables enable detection of these patterns, potentially allowing earlier treatment.

More accurate diagnosis

Continuous monitoring allows for better differentiation between true hypertension and temporary BP elevations, reducing misdiagnosis. Patients with elevated office BP (white coat hypertension) but normal readings at home can avoid unnecessary treatment. Those with normal clinic BP but high home readings (masked hypertension) can receive appropriate therapy before complications arise.

My blood pressure

I wore, and still wear, the Aktiia BP bracelet which is CE but not FDA-approved i.e. it’s available in Europe but not the United States or South Africa.

The bracelet (pictured below) initialises with arm cuff (supplied) inflations, which takes a few minutes. This process is repeated monthly. The Aktiia records a BP about 30 times in every 24 hour period, night and day, while the wearer is at rest, and stores the results for download to your phone.

Every morning, I diligently download the data to my phone.

The graph below shows that my BP started high, about 140/80, approximating the reading at the wellness check. About 2 weeks later, it was significantly lower and over the next 6-8 weeks it just about reached target levels, around 120 systolic (the upper number) or less, and about 70 diastolic.

What brought the BP down? From the start, I had resolved to get a little more sleep each night, exercise more frequently, and salt my food less. Whether these relatively small changes[3] over a short period of time truly made the difference, or whether the decrease was device related in some way, is an important question. So far, having checked some BP readings with the cuff as well as with another home BP device, and based on published validating studies which I’ll cover in another article, I believe the measurements to be accurate.

In the next graph, it’s easier to see the decrease in my systolic BP over the 2 month period. My current median systolic blood pressure – 121 mmHg – is just short of optimal (120 mm Hg or less). Two device re-initialisations were performed, on Day 5, and Day 34, as the manufacturer advises.

The graph below shows that my BP is lower at night – the so-called “evening dip” – and this is normal. Loss of the dip is an important indicator of cardiovascular risk. The Aktiia device has however been observed to significantly over-read, by as much as 15 mm Hg, at night (see below – shaded area of the graph). This is again reassuring as the measured decrease is short of the minimum normal difference of 10% but when corrected for the possible over-read, is about 17% lower than during the day, well within the 10-20% expected range.

Could personalised hypertension management reduce complications and healthcare costs?

Tailored medication

One of the biggest challenges in hypertension treatment is deciding the right medication and dosage for each patient. Wearable BP monitors provide detailed data – hundreds or thousands of data points – showing the blood pressure response to medications and other events throughout the day. Dosages can then be adjusted based on real-time BP trends rather than occasional office visits. Morning hypertension, often linked to higher stroke risk, can be detected and medications timed accordingly (“chronotherapy”). Unnecessary medication use in patients with borderline or well-controlled BP can be reduced.

Lifestyle changes

Lifestyle modifications – such as dietary improvements, exercise, and stress reduction – are often started before, or with, medicine. Their impact can be difficult to assess with limited BP readings. Continuous monitoring shows how specific changes affect BP in real-time, potentially improving adherence and motivation. For example, immediate BP reductions may be seen after a walk, reinforcing the benefits of exercise. The impact of dietary sodium intake can be tracked, leading to more adherence to dietary prescription. Stress-related BP spikes can be identified which might respond to relaxation techniques or behavioural interventions.

Predicting and preventing high blood pressure crises

Patients at risk of hypertensive crises (severe BP spikes that can lead to stroke or heart attack) can receive alerts and early warnings through their wearable devices. This could lead to timely medical intervention and prevent life-threatening complications.

Reducing hospital admissions and Emergency Department visits

By improving BP control and enabling early detection of dangerous trends, wearable BP monitoring could significantly reduce hospital admissions due to uncontrolled hypertension, potentially saving both lives and healthcare costs.

Challenges and future directions

Despite their promise, wearable BP monitors aren’t perfect, for example:

• Current devices still require calibration against traditional BP cuffs to ensure accuracy.
• Many devices are still undergoing validation and FDA/CE approval processes.
• Validation studies show systematic error, such as Aktiiia’s noted overestimation of night time blood pressure values.
• Widespread adoption depends on affordability and integration into routine care.
• Continuous BP tracking generates vast amounts of data, which can overwhelm clinicians and may require AI-driven analysis and clinical decision support systems to be put in place.

High quality clinical trials are needed before wide acceptance of wearable BP devices.

A new era for hypertension care?

Wearable BP devices enable earlier detection, better medication management, and enhanced lifestyle interventions, which should lead to better blood pressure control and reduced cardiovascular risk. They could transform the diagnosis and treatment of hypertension.

However, challenges remain, including affordability, and better evidence about improved health outcomes. Better sensor technology is needed to improve accuracy and eliminate the need for calibration. Device data must integrate with electronic health records (EHRs) and decision support may be needed to help clinicians interpret large amounts of data and make optimal treatment decisions.

With my wearable device, the question of whether Discovery’s coffee rewards are good or bad for my blood pressure could be answered. But on this measurement quest there are some things I’d still rather not know!

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[1] Photoplethysmography (PPG): a small sensor shines light onto your skin (like on your fingertip or wrist), and a detector measures how much light bounces back. Since blood absorbs light, changes in the reflected light help track your pulse and blood circulation. This technology is used in smartwatches, pulse oximeters, and devices that monitor heart rate and oxygen levels.

[2] Pulse Pressure Transit Time (PTT): the delay between electrical heart signals (ECG) and pulse wave arrival (detected using PPG).

[3]Unfortunately not documented – I wear a regular wristwatch on my left wrist, and consigned my Fitbit, which does measure sleep, to the bedside table.