Some people with darker skin tones have experienced inaccurate heart rate readings when using HR monitors. Research conducted recently at Duke University in Durham, North Carolina, showed that this malfunction—formerly an issue for some products—is now resolved.

“We started this study because we were seeing some evidence, both in research and anecdotally, that indicated wearable devices weren’t working as well for people with darker skin tones,” said Jessilyn Dunn, PhD, assistant professor of biomedical engineering at Duke. “People would compare a reading on a chest strap to their smartwatch and get different heart rate values. The companies that manufacture these devices don’t put out any metrics about how well they work across skin tones, so we wanted to collect evidence . . . .

“Previous research demonstrated that inaccurate PPG (photoplethysmography) heart rate measurements occur up to 15% more frequently in dark skin as compared to light skin,” said Dunn. “That’s because darker skin has a higher melanin content, and melanin absorbs the wavelength of light that PPG uses.” Dunn and colleagues examined data from (round 1) Empatica E4 and Apple Watch 4; (round 2) Fitbit® Charge 2; and (round 3) Garmin® Vivosmart® 3, Xiaomi Mi Band and Biovotion Everion®. The researchers concluded that many device software updates have addressed concerns related to skin tones.

Read the open-access study in npj Digital Medicine (2020; 3 [18]).