David Walsh, the computer scientist who developed AutoSleep, said he knew the movement and heart rate sensors would not accurately estimate the REM stage, so he didn’t bother. Another unknown for sleep trackers are the algorithms that are being used to measure people’s sleep, Dr. Vallat said. In contrast, the algorithms used by university sleep labs have been publicly shared for decades. Some scientists said consumer-grade sleep trackers should not be dismissed as inaccurate. The ring measures motion and heart rate to present granular data about the different sleep stages.

Source: New York Times July 17, 2019 12:56 UTC