Unpacking the Apple Watch's New Sleep Tracking Features: A Step Closer to Accurate REM and Deep Sleep Detection

In recent years, wearable devices have become increasingly popular for tracking our daily activities, from sleep patterns to exercise routines. Apple Watch is no exception, with its latest update promising to take a more granular approach to monitoring our sleep cycles. But what exactly does this mean for users? And how accurate can these devices really be?

According to Dan Gartenberg, CEO of SleepSpace and sleep scientist, devices like the Apple Watch use Photoplethysmography (PPG) to measure heart rate, which allows them to estimate brainwaves with around 80% accuracy. This is achieved by combining data from motion and heart rate sensors.

The new update to the Apple Watch's operating system will track users' sleep in a more detailed way, detecting when they are in REM, core, or deep sleep using signals from the accelerometer and heart rate sensor. Currently, the watch can only estimate sleep duration if 'Sleep Focus' is turned on, based on movement levels during sleep.

Dr. Azizi Seixas, director of the Media and Innovation Lab at University of Miami, uses multiple tracking devices himself and believes that these new tools provide valuable insights into our sleep health. He notes that healthy sleep is characterized by increased REM and deep sleep, which these devices can detect with reasonable accuracy.

While it's exciting to see advancements in sleep tracking technology, it's important to remember that no two wearables estimate behavior (like sleep and step count) the same way. This means users may be disappointed to find that fancy composite scores are often based on unvalidated algorithms.

The new Apple Watch app allows users to swipe between different sleep detection algorithms, including their own, Apple's, or other devices. This added layer of customization can help users better understand their unique sleep patterns and identify potential risks for serious sleep disorders.

As the tech giant continues to push the boundaries of wearable innovation, it will be interesting to see how these new features impact our understanding of sleep and its role in overall health. For now, with the Apple Watch's updated operating system, users can look forward to a more detailed picture of their nocturnal habits – and potentially even better sleep quality as a result.

Awake rem core deep apple watch