How are Heart Data from a Smartwatch and Skin Tone Related?

Consumers are increasingly using smartwatches and other wearable devices to measure their heart rate and rhythm and monitor their overall health during exercise. But according to a study presented at the 71st annual science session of the American College of Cardiology, those measurements may be less accurate in those with darker skin tones.

These findings are based on a systematic review of 10 previously published studies involving a total of 469 participants. This study is the first to collect data from a number of studies, specifically examining how skin tone can affect the accuracy of heart data on wearables.

‘Studies suggest that devices like smartwatches are less effective at tracking heart rate in people with darker skin tones than those with lighter skin tones.’

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“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 Daniel Koerber, MD, resident physician at the University of Alberta in Edmonton, Canada, and the study’s co-lead author. “Algorithms are often developed in homogeneous white populations, which may lead to results that are not as generalizable as we would like. 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.”

After screening 622 scientific documents, the researchers identified 10 studies that reported heart rate and rhythm data for consumer wearable technology based on participant's race or skin tone. Of those studies, four studies found that heart rate measurements were significantly less accurate in dark-skinned individuals compared to the measurements of verified devices such as lighter-colored individuals or chest strap monitors or electrocardiograms. While there is no difference in the accuracy of heart rate, one study suggests that wearable devices recorded significantly lower data points for those with darker skin.

Most wearables detect the heartbeat and rhythm and target a beam of light on the wrist, which then detects how much light is being absorbed. Excessive light absorption indicates excessive blood flow through the veins under the skin. Study results show that this signaling process does not work on dark skin that is high in light-absorbing melanin.

With the increasing use of consumer wearable items to monitor physical activity and sleep patterns, there has been a growing interest in recent years in the use of these for medical research and for early detection of heart problems.

“There are a lot of claims that these devices can detect heart rhythm issues like tachycardia, bradycardia and even atrial fibrillation,” Koerber said. “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.”

This study underscores the importance of ensuring that technology meets the needs of a diverse population, especially when it aims to improve health. Other devices, such as pulse oximeters used to measure the level of oxygen in the blood, do not work for people with darker skin color, and recent studies suggest that this can lead to serious health consequences if complications are not detected.

“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. "For example, there is some evidence to suggest that certain wavelengths of light, particularly green light, are more accurate in people across all skin tones," he said.

As a systematic review, the research was limited by a relatively small number of relevant published studies and the variability of the estimated population, devices, and effects in different studies.

Source-Medindia