Watch AI flags high blood pressure but can't replace a cuff

Many people with high blood pressure have no idea, because the condition often shows no symptoms early on. They find out when someone happens to measure it, or when something has already gone wrong. More than half of adults with high blood pressure do not know they have it. That is the problem Google's researchers are trying to solve with a watch many people already wear.

The team built an AI that reads data from an ordinary smartwatch and estimates whether the wearer shows signs of high blood pressure. The Decoder reported that the work was published in the journal Nature. It is worth knowing about, but it is still research, not a feature people in Thailand can switch on today.

The AI reads pulse and movement and gives a likelihood, not a blood pressure number

The watch needs only two sensors that most smartwatches already have: one that shines light into the skin under the wrist to count the pulse, and one that tracks arm movement. In Google Research's blog post, the system needs no arm cuff to calibrate it before use, and it also takes the wearer's height as an input.

The AI trained on 492,347 hours of sensor data from 2,109 participants, without anyone telling it in advance who had high blood pressure. It learned each person's pulse patterns on its own, then averaged several days of data into a likelihood of high blood pressure. The output is a warning that blood pressure is probably high, not a figure like 130/80 that can be compared with a threshold.

In a test of 196 people the watch caught 65.8%, a single clinic check 55.3%

The results come from 196 adults at five research sites in the US. The team had everyone wear a blood pressure monitor for 24 hours, the standard doctors use to confirm the condition, as the answer key for who truly had high blood pressure. They then counted how many of those people the watch and a single clinic check caught.

The watch caught 65.8% of people with high blood pressure, and a single clinic check caught 55.3%. For people with normal blood pressure, the watch correctly said normal about 90% of the time. Put simply, the watch caught about two in three people with high blood pressure, still missed about one in three, and about one in ten people with normal pressure could get a false warning.

Another figure worth reading alongside comes from a subgroup of 48 people whose first clinic reading was high. The watch caught 78.4%, a repeat clinic check caught 67.6%, but measuring at home over several days caught 89.2%, higher than the watch.

It is still research, and Google says it does not replace a cuff

Google says the method does not replace an arm cuff and is not a diagnosis on its own. The work is an early feasibility study, and the methods are experimental, with no word on any product in use or on the way.

Every participant had no known cardiovascular disease and was not taking blood pressure medicine, so it is not yet known whether the results would hold for people already on medication or with other conditions.

There are reports that the research has been applied to the blood pressure trends feature in the Google Health app, but the pages read name no watch model and list no countries where it works. Anyone wearing a smartwatch should check with the maker of their own model.

Measure at home the way the Department of Disease Control describes

The Department of Disease Control counts blood pressure as high from 140/90 mmHg when measured at a medical facility. The top number is the pressure when the heart squeezes, and the bottom one is when it relaxes. When people measure themselves at home with a portable device, the threshold drops to 135/85, according to the Q&A on high blood pressure indicators from the department's Division of Non-Communicable Diseases. If the home and clinic results disagree, that document says to go by the home result, because it predicts heart and blood vessel complications better.

The method is to sit with both feet flat on the floor and rest at least 2 minutes before measuring. Measure twice a day. In the morning, do it within 1 hour of waking and after urinating, before breakfast and before any medicine. In the evening, do it before bed. Each time, take at least two readings 1 minute apart, for 7 days in a row or at least 3 days.

If you have no device at home, try asking a pharmacy, a clinic or a community health station near you whether they have one you can use. One high reading alone tells you little, because the Department of Disease Control's page on high blood pressure explains that blood pressure rises and falls all the time, so you cannot diagnose yourself and a doctor has to decide whether you have the disease.

When to see a doctor, and why not to wait for symptoms

Patients may have no symptoms at all. Some get headaches, confusion, dizziness or unusual tiredness. Having no symptoms does not mean blood pressure is normal, and left alone the condition can lead to heart failure, a burst or blocked blood vessel in the brain, heart attack and kidney failure.

If a reading is 140 to 179 on the top number or 90 to 109 on the bottom, a doctor will have you measure at home for at least 7 more days or book a repeat reading at the same place before confirming the disease. At 180/110 or above, the doctor considers confirming the diagnosis that day or the next, so it should not wait.

What you can do today: if you have never measured your blood pressure properly, start measuring morning and evening for 3 days using the steps above, write the numbers down, and if any day reaches the 135/85 line, take your notes to a doctor. If you already wear a smartwatch you can use it to watch trends, but the numbers you can rely on still come from an arm cuff device.

FAQ

Can a smartwatch measure blood pressure instead of a cuff yet?

Not yet. Google says the method does not replace an arm cuff and is not a diagnosis, and it is early-stage research.

How accurate was Google's AI at finding high blood pressure?

In a test of 196 people in the US, the watch caught 65.8% of people with high blood pressure, and a single clinic check caught 55.3%. It still missed about one in three.

What counts as high blood pressure under the Department of Disease Control?

140/90 mmHg or above when measured at a medical facility, and 135/85 or above when measured at home with a portable device. A doctor has to make the diagnosis.

Can people in Thailand use this feature yet?

There is no confirmation. The sources read name no watch model and list no countries where it works.

Sources

• Google Research: detecting signs of hypertension using wearable sensors
• The Decoder: Google's AI detects high blood pressure from a regular smartwatch without a cuff
• Department of Disease Control: Q&A on diabetes and high blood pressure indicators (Division of Non-Communicable Diseases, 2022)
• Department of Disease Control: high blood pressure