How accurate your smartwatch health data is depends on your skin tone: Canadian study

A man is seen using a smartwatch in this stock photo. (Pexels)

A new Canadian study has found that smartwatches are less effective at tracking the heart data of people with darker skin tones.

The study, conducted by researchers at the University of Toronto, found that smartwatches and other wearable devices used to measure heart rate and rhythm during exercise may not accurately track this data in people of colour.

According to researchers, most consumer wearable technology monitors heart rate and other health data by aiming a beam of light at the wrist and then detecting how much light is absorbed.

A greater light absorption indicates a greater volume of blood flow, and researchers suggest this signalling process might not work as well in darker skin that contains more melanin, which absorbs light.

"People need to be aware that there are some limitations for people with darker skin tones when using these devices, and the results should be taken with a grain of salt," said study co-lead author Dr. Daniel Koerber, who is now a resident physician at the University of Alberta, in a press release.

The findings, which will be presented at the American College of Cardiology’s Annual Scientific Session in April, are based on a systematic review of 10 previously published studies that reported smartwatch heart rate and rhythm data according to a participant's race or skin tone.

The 10 studies involved a combined total of 469 participants.

Of these studies, four found that heart rate measurements were "significantly less accurate" in darker-skinned participants when compared to lighter-skinned individuals, as well as measurements from a medically-validated blood pressure device, including chest strap monitors or electrocardiograms.

According to researchers, one study reported that although there was no difference in heart rate accuracy, wearable devices recorded "significantly fewer" data points in achieving one's daily health goals in those with darker skin tones.

While the use of smartwatches and fitness trackers to monitor physical activity and sleep patterns has grown in recent years, the study notes there has also been an increased interest in using consumer wearables for medical research in the early detection of heart problems.

However, researchers say inaccurate readings for people of colour would hamper this.

"There are a lot of claims that these devices can detect heart rhythm issues like tachycardia, bradycardia and even atrial fibrillation," Koerber said in the release. "We want to be able to inform health-care providers about whether these are reliable sources for collecting data in all patients, regardless of skin tone."

Koerber said the findings highlight the need to ensure that technology meets the needs of diverse populations, especially when it comes to improved health. He said other studies have shown that pulse oximeters, which are used to measure the amount of oxygen in the blood, also do not work as well on people of colour.

He added that this could lead to serious consequences if health problems in diverse populations go undetected.

"It is important to explore alternative options to make sure we can create a more equitable solution in health care and not just in the consumer industry," Koerber said.

One solution, he said, is to use different wavelengths of light in wearables, such as green light, with evidence suggesting it can more accurately monitor heart data in people across all skin tones.

Despite the findings being the first to combine data from multiple studies to examine how skin tone may affect the accuracy of heart data in smartwatches, the study's authors say more research is needed.

As a systematic review, researchers note the study was limited by the small number of relevant published studies on the topic, as well as the variability in the populations, devices and outcomes assessed in these different studies.

Koerber said in the release that algorithms for wearables are "often developed in homogeneous white populations," which may lead to results that are less generally applicable.

"Ongoing research and development of these devices should emphasize the inclusion of populations of all skin tones so that the developed algorithms can best accommodate for variations in innate skin light absorption," he said.