Self-tracking: what watches can measure

Displaying the pulse, recording an ECG, assessing the rhythm - can a digital watch already protect patients from strokes? A study shows the opportunities and risks of collecting data yourself

Heart rate measurement: Not only athletes rely on intelligent watches

© Getty Images / Hoxton / Ryan Lees

They measure the pulse, monitor sleep, count the steps. Now they are also supposed to detect cardiac arrhythmias - without any medical intervention. Smartphones, intelligent digital watches and other mini-computers collect more and more data about our health. Above all, the manufacturers and operators of these products benefit from this.

Digital treasures

"Patient data is the new gold and the essential business foundation for digitization," says Professor Peter Radke, chairman of the "Digital and Mobile Health" committee of the German Cardiac Society. With this data, the corporations would be able to offer sick people specially tailored offers, for example care by doctors who are employed by them.

To do this, however, the data collected must be reliable. An occasion for the US company Apple to check whether its watch actually recognizes atrial fibrillation. Atrial fibrillation is the most common cardiac arrhythmia and is also responsible for around a quarter of all strokes. Often, however, the patients do not feel any of it. Could a digital watch warn you of the risk?

How the clocks record the heartbeat

A diode on the back of the watch being examined sends light through the skin. The distance between two heartbeats can be measured using the reflection from the small blood vessels. If the pulse is irregular for no external reason, this is a possible sign of atrial fibrillation.

The result of the study, in which 420,000 people took part and which included doctors from Stanford University Hospital: In around 0.5 percent of the participants, the watch actually reported an irregular pulse, especially in the elderly. A subsequent ECG only confirmed the suspicion of atrial fibrillation in every third case. This is probably also due to the fact that the arrhythmia often only occurs in episodes - not necessarily exactly when the doctor is recording an EKG.

Atypical patients

The majority of the study participants did not correspond to the typical atrial fibrillation patient: average age 40 years, no symptoms of heart disease. However, the medical guideline for atrial fibrillation recommends an examination for the disorder without suspicion only for people aged 65 and over and for everyone who has already suffered a stroke. Because anticoagulant drugs could protect them from another cerebral infarction.

However, the remedies also carry the risk of severe bleeding. It is unclear whether the benefit outweighs this risk, especially in younger patients - especially if the diagnosis was based on a measurement without cause.

Are anticoagulants used too soon?

In practice, however, this is not always taken into account. "Patients are often already receiving anticoagulants when, for example, a pacemaker indicates rapid atrial beats," reports Professor Paulus Kirchhof, director of the Institute for Cardiovascular Science at the University of Birmingham (England). In the future, this will be the case even more frequently due to the further spread of digital devices - despite the current status of the unclear benefit.

Cardiologists also worry about messages from the watch that a long-term ECG does not confirm. What should you advise these people? Therapy is not popular with them, but they still have to live with suspicion. "A lot of measurements without consequences rather unsettle some patients than calm them down," says Peter Radke.

Professor Gerhard Hindricks, medical director of the Leipzig Heart Center, is also critical of the random collection of heart data. He finds something else both breathtaking and terrifying: the entire study up to the evaluation of the ECG was carried out solely under the direction of the manufacturer. Only when the EKG was abnormal did people see a flesh-and-blood doctor. "Our healthcare system is not prepared to use this technology, which is beneficial if used correctly," says Hindricks. And the development continues.

A simple EKG can be recorded with the latest generation of digital clocks

© W & B / Astrid Zacharias

Left alone with numbers

The latest generations of digital clocks already allow a simple EKG measurement; the collection of further heart parameters is close at hand, the measurement of the blood sugar content without peaks is another goal. Such a flood of data, however, not only harbors opportunities, but also the risk of incorrect therapies.

That is why the field should not be left to the companies, says Hindricks. "We have to talk about how to use such techniques sensibly and embed them in existing health structures. Doctors, clinics, pharmacies, health insurance companies and patient associations need to be on board." The cardiologist wants to set up a center in Leipzig where doctors advise patients and help them deal with the data appropriately. The numbers alone can be misleading.