SAN FRANCISCO (Reuters) - Apple Watch Series 11 models that go on sale on Friday can notify users that they may have high blood pressure, in a feature the company has powered using artificial intelligence rather than a blood pressure monitor.

The notification feature, which will work with models back to the Apple Watch Series 9, came about from applying AI models to existing sensor data, said Sumbul Ahmad Desai, Apple's ( AAPL ) vice president of health.

Apple ( AAPL ) had been interested for years in trying to identify high blood pressure, she told Reuters.

The condition affects more than 1 billion people globally, but half of the adults with it go undiagnosed, in part because the standard for measuring blood pressure - a cuff called a sphygmomanometer - is something many people encounter only at a doctor's office.

Apple ( AAPL ) used AI to sort through the data from 100,000 people enrolled in a heart and movement study it originally launched in 2019 to see whether it could find features in the signal data from the watch's main heart-related sensor that it could then match up with traditional blood pressure measurements, Desai said.

After multiple layers of machine learning, Apple ( AAPL ) came up with an algorithm that it then validated with a specific study of 2,000 participants.

Apple's ( AAPL ) privacy measures mean that "one of the ironies here is we don't get a lot of data" outside of the context of large-scale studies, Desai said. But data from those studies "gives us a sense of, scientifically, what are some other signals that are worth pulling the thread on ... those studies are incredibly powerful."

The feature, which received approval from the U.S. Food and Drug Administration, does not measure blood pressure directly, but notifies users that they may have high blood pressure and encourages them to use a cuff to measure it and talk to a doctor. 

Apple ( AAPL ) plans to roll out the feature to more than 150 countries, which Ami Bhatt, chief innovation officer of the American College of Cardiology, said could help people discover high blood pressure early and reduce related conditions such as heart attacks, strokes and kidney disease.

Bhatt, who said her views are her own and do not represent those of the college, said Apple ( AAPL ) appears to have been careful to avoid false positives that might alarm users. But she said the iPhone maker should emphasize that the new feature is no substitute for traditional measurements and professional diagnosis.

"There is also the risk of false reassurance - those who don't get an alert may wrongly assume they don't have hypertension," Bhatt said in an interview.