How does the Oura Ring determine when you fall asleep?

The Oura Ring determines sleep onset by monitoring a range of physiological signals through sensors embedded in the ring. These sensors measure the wearer's body temperature, heart rate variability (HRV), resting heart rate, and movement using a 3D accelerometer and gyroscope. When one lies down to rest, there are distinct physiological changes: heart rate slows, HRV patterns change, body temperature drops slightly, and movements become less frequent and more regular as one enters the different stages of sleep. The Oura Ring's algorithms analyze these biometric patterns to detect shifts consistent with sleep. By recognizing these changes, the Oura Ring is able to deduce when the wearer has transitioned from wakefulness into sleep.