Apple will offer in South Korea a feature that detects signs of chronic high blood pressure and notifies users. Apple said on Jan. 28 that the Apple Watch "high blood pressure notification" feature is now available in South Korea.

When users set up the feature in the Health app, an algorithm analyses data in the background for 30 days. If signs of chronic high blood pressure are found, it sends a notification to the user. Apple Watch collects information on blood vessel response to heartbeats using photoplethysmography (PPG).

Apple said the feature’s performance was validated in a clinical study involving more than 2,000 people. It said it developed the algorithm using data from more than 100,000 study participants. It received approval from the U.S. Food and Drug Administration (FDA).

The algorithm collects 60 seconds of PPG signals about every 2 hours during waking hours. It processes data only when the user is sitting still. Apple recommends that users who receive a high blood pressure notification record blood pressure for 7 days with a third-party blood pressure monitor and share the results with medical staff.

The feature does not directly measure blood pressure and does not provide blood pressure values to users. Use is restricted for those under 22, people who have previously been diagnosed with high blood pressure, and pregnant women. Supported devices are Apple Watch Series 9 and later and Apple Watch Ultra 2 and later. Apple Watch SE is excluded.

Apple said, "Even wearing an Apple Watch for 30 days can indicate the possibility of high blood pressure," and "It detects signs of high blood pressure on your wrist that could be missed for years."