What Wearables Can (and Can’t) Tell You About Your Heart Health

Summary

Wearable devices such as fitness trackers and smartwatches are now widely used to monitor heart health, capturing data on heart rate, activity, sleep and blood oxygen. The article explains how photoplethysmography (PPG) and electrocardiographic (ECG) data from these devices can help track trends and potentially support clinical decisions, including detecting abnormal rhythms. However, it cautions that wearables have significant limitations: BP measurements based on wearables may lack cuff validation, data standardisation across devices is inconsistent, and many wearables are not officially medical devices. While promising for ongoing monitoring and integration with cardiology, the piece emphasises that wearables should not replace medical examination or diagnosis. NHS plans to mainstream wearables by 2035 depend on data quality and interoperability. Author: Nature

What wearables can (and can’t) tell you about your heart health

Half of people in the UK use a wearable device, such as a fitness tracker or smartwatch. These devices collect data relating to health and physical activity levels – including heart rate, step count and sleep quality. With the emergence of AI, such devices will probably become even more sophisticated – potentially able to diagnose our health problems before our GP.

But while wearables can be really useful when it comes to understanding many aspects of your heart health, they still have many shortcomings – so it’s important not to rely on them for everything.

A key strength of modern wearables is the fact that they record such a wide range of useful data, and track trends over time. This makes them perfect for measuring whether any lifestyle changes you’ve made are working for you, and what effects they might be having. For instance, your wearable can tell you if your health kick has had a measurable affect on your sleep quality or blood pressure.

In addition to measuring step count and physical activity, many of the most commonly worn wearables collect cardiovascular data via photoplethysmography (PPG). This is where a light located at the back of the wearable interacts with tiny blood vessels in the skin to give an estimate of changes in blood volume. These changes can be used to accurately measure heart rate, rhythm and blood oxygen levels.

Many currently available devices are also able to record electrocardiographic (ECG) data. This also records your heart’s electric activity, including heart rate and rhythm.

This is why some wearables, particularly those with ECG technology, could be useful in cardiology consultations.

Wearables may even be able to detect abnormal heart rhythms. Melnikov Dmitriy/ Shutterstock

For instance, a recent study demonstrated that smartwatches can reliably detect atrial fibrillation (a heart rhythm disorder that increases risk of stroke) in patients at risk of the condition. And wearables can also be useful for regularly and accurately monitoring daytime blood pressure.

So, wearables have the ability to provide data that is highly useful to a cardiologist in helping determine a probable diagnosis. But just how much can we rely on this data?

Wearable limitations

Most wearables that detect blood pressure do so via PPG data, which measures blood pressure differently to an inflatable blood pressure cuff. Wearables may also only provide a blood pressure range rather than absolute results. This means a patient may not know whether their “true” blood pressure is normal or not.

The British and Irish Hypertension Society, which formally validates and endorses cuff-based blood pressure monitors, currently doesn’t have a framework to validate wearables. This means no wearables on the market which provide blood pressure monitoring have been officially validated.

There’s also a lack of standardisation across the market for how different wearables produce data for particular metrics. This means it’s possible different devices could give different readouts – even if they’re looking at the same person. If wearables are to be integrated into the healthcare system in future, then standardised, validated methods would be needed.

There are also potential issues in how wearables are positioned within the market with regard their medical capabilities.

Some are advertised as having medical-grade measuring capabilities. However, the majority of devices on the market have not been approved as medical devices by regulatory bodies. This distinction is important for the average consumer to understand, so they don’t trust the device’s data more than they should.

While wearables can be extremely useful for understanding many aspects of your day-to-day heart health, there’s still much about them that will need to be improved before they become a standard part of cardiac care.

Quality assurance and compatibility across different brands will be key, as will ensuring a patient’s data is both reliable and accessible to healthcare staff on their electronic health records.

These are important issues that must be addressed soon if wearable technology is to become a standard part of NHS treatment by 2035, as outlined in the NHS’s ten-year plan for England.