This story from STAT shows how well documented (study 1, study 2) properties of the green lights used in consumer mHealth devices may not work as well with users who have darker skin. Apple uses both green light and infrared light in its sensors which may make it more accurate (but no studies have been done on this according to the article -Ed.).
But they also emphasized that the effect of melanin on green light absorption is well-documented — and that without more research or more public information from the manufacturers about accuracy, it is equally hard to prove there isn’t an impact.
The issue may be that people with darker skin tones are not being represented in studies. The article goes on to describe one study that recruited a diverse population:
Just one study, a 2017 paper published in the Journal of Personalized Medicine, teased out the error rates for a host of devices that were on the market at that time. It found that while the technologies were “within acceptable error range” in most settings, device error was higher for those with a darker skin tone.
The article names the devices which seemed to suffer from these issues and the devices which did not.
This story serves as a reminder that diversity in studies and trials is critical to ensure that the products being produced work for everyone in the population.