Smartwatch Heart Data Depends on Skin tone, Findings of Studies Show


Measurements may not be accurate in those with darker tones, according to analysis to be presented at the American College of Cardiology’s 71st Annual Scientific Session.

Although smartwatches and other wearable devices are beneficial to measure heart rate and rhythm during exercise, these measurements may not be accurate in individuals with darker skin tones, according to the results of studies to be presented at the American College of Cardiology’s 71st Annual Scientific Session.

The results are based on a systematic review of 10 previously published studies involving a total of 469 participants and is the first to pool data from multiple studies to explicitly examine how skin tone may affect the accuracy of heart data in wearables, according to the study authors.

“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,” study co-lead author Daniel Koerber, MD, resident physician at the University of Alberta in Edmonton, Canada, said in a statement.

“Algorithms are often developed in homogeneous white populations, which may lead to results that are not as generalizable as we would like,” he said. “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.”

The research team identified 10 studies that reported heart rate and rhythm data for consumer wearable technology according to the participant’s race or skin tone. Of these studies, the results of 4 showed that heart rate measurements were significantly less accurate in darker-skinned individuals compared with either light-skinned individuals or measurements from validated devices, such as chest strap monitors or electrocardiograms. In 1 study, though there was no significant difference in heart rate accuracy, wearable devices recorded significantly fewer data points for individuals with darker skin.

In many wearable watches, heart rate and rhythm are detected by aiming a beam of light at the wrist and then detecting how much light is absorbed. With this, a greater light absorption indicates a greater volume of blood flowing through the veins under the skin.

Investigators suggest that the signaling process may not work as well in darker skin that contains more melanin, which absorbs light.

“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.”

The results of recent studies have shown how other devices, such as pulse oximeters used to measure the amount of oxygen in the blood, do not perform as well for individuals with darker skin tones, which can end in more serious health consequences if problems go undetected, Koerber said.

“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.

As for study limitations, the studies used a relatively small number of relevant published studies, as well as the variability in the devices, outcomes, and populations assessed in different studies.


How accurate is smartwatch heart-data? It depends on your skin tone. American College of Cardiology. News release. March 23, 2022. Accessed March 30, 2022.

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