Your phone, smartwatch or temporary tattoo may not be accurately reading your blood pressure, UW study says

If you track your blood pressure with your phone or smartwatch, you may want to think again.

According to a new study from the University of Washington, many of these newer devices claiming to measure blood pressure have not been properly vetted and may be giving consumers inaccurate readings. These blood pressure measuring devices or apps include phones, watches, rings, patches and even temporary tattoos.

These cuffless devices have entered the market in recent years and claim to be a more convenient alternative to traditional cuff blood pressure monitors that squeeze your upper arm or wrist.

“There are hundreds of devices available on the market that you can buy on Amazon, and they claim to accurately measure blood pressure. Our intent is to show we’re not ready for those types of devices to be used for clinical purposes because their accuracy has not been validated,” said study lead author and UW cardiologist Dr. Eugene Yang.

In independent studies of these devices, they are sometimes up to 15 millimeters of mercury off of an actual blood pressure reading. For a blood pressure measurement device to be accurate, it must be within 5 millimeters of mercury to the actual blood pressure. Any more, and that difference may make someone who has high blood pressure believe their reading is normal.

“If your blood pressure is 20 points higher than it should be, your risk of dying from a heart attack rises twofold. So being off by 15 points means your risk of dying could be up to 1.7 times higher,” Yang said.

MultiCare Pulse Heart Institute cardiologist Dr. Mohit Jain called blood pressure a “silent killer” that most people need to track better.

High blood pressure is typically caused by arteries becoming less able to carry blood effectively. The condition often arises from genetic factors, age or obesity. Complications of high blood pressure include increased risk of stroke, heart attacks, heart failure and kidney damage.

Jain noted it is most important for patients to get accurate readings at home because those readings are more precise than in office visits where stress may inflate an individual’s typical blood pressure.

“Blood pressure is important. More people need to pay attention to it. It’s easy, it’s cheap to do with a cuff. And there’s a lot of variable technologies that are coming through, but I’m a little bit skeptical about how accurate those technologies are,” Jain said.

Traditional cuff measurement devices use inflatable cuffs to detect subtle vibrations or “oscillations” in your arm’s brachial artery. These devices technically do not measure blood pressure but rather convert that oscillation data into a digital estimate of blood pressure, Yang said.

In contrast, many of these newer devices or apps use artificial intelligence to estimate blood pressure. The exact method these devices use to measure blood pressure is often unknown because the companies behind them are using proprietary algorithms to estimate blood pressure.

Some devices are easier to understand, like how a smartwatch’s sensors detect changes in your wrist or a ring measuring the blood vessels in your finger. But another method is a temporary graphene tattoo. These stickers adhere to the skin of the forearm and measure blood pressure.

Yang’s research aims to create a monitor that can measure blood pressure from a video or picture. That way, doctors could more easily measure blood pressure for those in quarantine. He does not think his technology is ready to be used, though.

Yang believes many of these methods to be exciting technology that may revolutionize how blood pressure is measured. But these AI-powered devices are not ready to be on the market.

Yang hopes many of these devices will be ready for market in the next five years. But until then, he wishes private companies would stop selling them.

“The technologies are exciting. More and more devices are being developed, but we need to step back and realize that until these technologies are validated, we need to use the conventional cuff devices,” he said.