At the Worldwide Developer Conference (WWDC) last week, the latest version of Apple’s operating system for wearables, watchOS 9, introduced several new features and refreshed the watch faces. In an interaction with TechCrunch’s Darrell Etherington, three senior Apple staffers share more insight about the latest health and wellbeing features baked into watchOS 9.

Apple’s VP of Health, Dr. Sumbul Desai, Chief Operating Officer Jeff Williams, and Fitness Technologies VP Jay Blahnik interacted with the publication. The conversation mostly revolved around new Apple Watch features such as Atrial Fibrillation (AFib) History, the Workout app, and sleep tracking. Williams started by explaining how these new features came about.

“It started when we were working on the watch. And because the watch was such a personal device, and you’re wearing it, we thought that there is a huge opportunity to maybe give people information about their health, and the more we started pulling on threads, we decided that not only is there an opportunity — there’s a responsibility to do more in the health space.”

AFib History

The new AFib History feature in watchOS 9 allows users to understand how often they are in a state of cardiac arrhythmia. Apple says the feature helps patients aged 22 or older diagnosed with Atrial Fibrillation. Detecting the condition early is critical because it is one of the leading conditions which eventually leads to a stroke.

Desai explained that the AFib History feature received FDA approval in the US. Its results on the Apple Watch were validated through a clinical study too. The accomplishment is significant for a piece of wrist-worn consumer technology which isn’t specialized cardiac monitoring equipment.

“As Jeff alluded to, everything we do in health is based on the science, and AFib History was validated in a clinical study, with participants wearing both Apple Watch and an FDA-cleared reference device. In that study, the average difference in weekly measurements between the two devices is actually less than 1 percent.”

Williams added that AFib History could be an asset to patients receiving ablation treatment for chronic fibrillation, especially if the treatment doesn’t succeed in its first run. However, he understood that the feature “will take some time” to be “understood, used, and adopted.”

According to Apple, the availability of the AFib History feature will be limited at launch, meaning it won’t be available in all markets and regions where the Apple Watch is sold.

Sleep Tracking

watchOS 9 allows tracking how much time you spent in different states of your sleep, namely REM sleep, Deep sleep, Core sleep, and how long you were awake. Williams prefaced the background of this feature, saying Apple isn’t the first to implement stage-wise sleep tracking.

“Prior to sleep stages, we were really focused on helping people meet their sleep duration goals since that’s really important — that consistency — but we wanted to go a little further and dig into the science, and provide users with more information around their sleep cycles. So using the signals from Apple Watch’s accelerometer and heart rate sensor, users will now be able to see their sleep stages while they’re in REM, core, and deep sleep.”

Besides these significant improvements, Apple also refreshed the existing watch faces and introduced new ones with watchOS 9. The update is available to developers in beta and will be rolled out to compatible Apple Watches this fall.