Despite growing popularity, a Veterans Affairs researcher cautions that the accuracy of fitness trackers may depend on the color of your skin.
Watches put out by Apple and Fitbit other companies are starting to measure more data useful to researchers and doctors.
Dr. Peter Colvonen works at the VA San Diego and he is an assistant clinical professor of psychiatry at UC San Diego. He’s the lead author of an editorial in the September edition of the journal Sleep where he warns his colleagues that these consumer-grade devices may not be accurate for people of color.
The issue is the green light used by most consumer devices.
“The problem is your skin and various skin tones absorb light differently and that throws off the algorithm that are getting used,” Colvonen said. “And what we are seeing is that the green light technology giving incorrect readings or not reading at all with the darker skin tones.”
The green light penetrates the skin. The light is absorbed by red blood cells and an algorithm uses the data to calculate heart rate. There hasn’t been enough research to prove the green light technology works the same for everyone. According to a small number of studies, the watches may not only be less accurate with darker skin tones but maybe less accurate through sweat or even tattoos, Colvonen said.
The limited amount of research on the watches often uses an outdated model, the Fitzpatrick Skin Type scale, developed in 1975, which reduces all skin tones to six colors, he said.
“All the skin tones of the world and you try to classify them in six skin tones. You’re missing a lot of data about the variances of skin tone,” Colvonen said.
As makers of the trackers press the Food and Drug Administration to approve data from their products to be used in research, Colvonen said researchers should be careful that they won’t include data which could be biased against people of color, before the data is is folded into research studies that may pull data from potentially hundreds of thousands of subjects.
“So these historical disparities are getting locked into these medical-grade components,” he said.
Apple’s latest watch advertises that it offers red and infrared — which is more expensive but more accurate, Colvonen said.
The majority of fitness trackers still use the cheaper green light, including Amazon Halo.
