Apple has expanded its sleep apnea notification feature to Apple Watch users in South Korea, the company announced today.

Sleep apnea is a condition in which breathing repeatedly stops and starts during sleep, often leading to poor rest. The Apple Watch detects signs of the disorder by using its accelerometer to track subtle wrist movements associated with irregular breathing patterns. When these disturbances occur repeatedly across several nights, the watch can flag a potential case of sleep apnea.

The…