Some apps promise to measure blood pressure entirely without any auxiliary tools. But is this really possible? We examined how these apps are supposed to work and whether they can deliver their promises.
How it's supposed to work
Generally speaking, blood pressure measurement works the same way in all commercially available devices: the inflation of the cuff makes it possible to measure the vibrations of the arterial walls.
Some apps promise to read blood pressure only by using the smartphone’s camera and microphone. The measuring procedure usually looks like this: First, the right index finger must be placed on the lens and the flash of the iPhone’s camera. Then the bottom of the iPhone, more precisely the microphone, must be pressed with direct contact to the chest. This position then must be maintained until the result of the measurement is concluded.
We have made it our mission to put these apps to a fact check. For our test we used three apps available on the Apple App Store. Striking is right at the beginning that all of these apps aggressively try to sell an often very expensive premium version via in-app-purchase (up to € 110 / year).
Undeterred, we continue the app test and find that two out of the three apps are not able to measure blood pressure at all, even though it is stated so in the App Store description. Instead, only a reading for the pulse appears. The third app, however, gives a blood pressure reading - first when we put the iPhone camera on our skin, and again when we hold it against a lifeless pillow. The accuracy of these blood pressure measurements can therefore be questioned.
In 2016, the Johns Hopkins University School of Medicine published an independent test of one of these apps, with devastating results. For example, 77.5% of all reading of patients with hypertension (blood pressure values above 140/90 mmHg) were found to be inaccurate. Overall, the measured values by the app differed from the real values on average by 12.4 mmHg systolic and 10.1 mmHg diastolic.
In addition, the company behind this app was sued in 2016 by the US Federal Trade Commission (FTC) due to false statements in the distribution and marketing of the App. The indictment was later resolved in a settlement. Unfortunately, we could not test this app as it is no longer available in Europe.
So, based on our test results, we would like to issue a warning: the resources available to current smartphones do not seem to be sufficient for reliable and accurate blood pressure readings. Take care that you do not accidentally become victim of subscription traps and do not use apps from dubious providers, because they could spy on your data.
Even if blood pressure measurement via app is currently not possible, it is worthwhile to measure your blood pressure regularly and monitor it via an app in the long term. Health apps such as Cora Health show you your long-term blood pressure data and display your average values.
Tip: The Cora Health app helps you track your blood pressure and encourages you to improve your heart health through scientifically-backed lifestyle recommendations.
Blood pressure monitors with Bluetooth
A trusted alternative for monitoring blood pressure on the iPhone are blood pressure monitors with Bluetooth and Apple Health Integration. These devices typically deliver blood pressure readings via Bluetooth to the chosen health apps, which in turn can be shared with apps like Cora Health using the Apple Health interface.
Here you can find a list of recommended blood pressure monitors
Measuring blood pressure with Apple Watch
At the moment, blood pressure can not be measured reliably with the Apple Watch, just as with the iPhone. However, rumors and patent applications are increasingly suggesting that Apple is developing wristbands for the Apple Watch that can measure health data such as blood sugar and blood pressure.
As there's no official information from Apple so far, we have to be patient and wait for future announcements. In the meantime, bluetooth blood pressure monitors paired with a blood pressure app are a proven alternative.