For sleep tracking, you’ve all heard me rave about the Oura ring, and probably the only reason I don’t use my Apple Watch for this purpose is because I love the comfort a ring provides as opposed to a watch.
But it doesn’t mean Apple can’t offer benefits when it comes to tracking my sleep. So, let’s dive into the facts and my own observations as to how accurate the Apple Watch’s sleep tracking is.
What the Research Says:
- Based on a study published in JMIR mHealth and uHealth, the Apple Watch Series 8 had a fair level of agreement with polysomnography (κ=0.2976) in sleep stage classification. This makes it a decent sleep tracker, but Fitbit Sense 2 and Galaxy Watch 5 were better, with a slightly higher level of agreement.
- Another study by Jaworski and Park (2023) tracked the Apple Watch Series 8’s performance in sleep tracking as compared to clinically validated actigraphy, ballistocardiography and polysomnography. It concluded that while the Apple Watch was effective in identifying sleep-wake states, it faced challenges in accurately distinguishing between sleep stages when compared to the reference polysomnography (PSG) system.
- Roomkham S, Hittle M, and Cheung J et al., in their research comparing a clinically validated actigraph with the Apple Watch for sleep monitoring, detected 97% accuracy and 99% sensitivity for detecting actigraphy-defined sleep and adequate specificity (79%) in detecting actigraphy defined wakefulness, over a period of 27 nights.
- A Validation of Six Wearable Devices for Estimating Sleep, Heart Rate, and Heart Rate Variability in Healthy Adults found 97% accuracy for sleep, 26% for wake, with an overall kappa value of 0.30 categorized into fair agreement. It, however, overestimated total sleep by 39.5 minutes on average, only 44% accuracy for light sleep, 71% for non-REM and REM, and 26% for wake. Wake was also misclassified as light sleep in 51% of cases.
Even the Quantified Scientist on YouTube found the Apple Watch post-WatchOS 9 update to be the best-performing sleep tracker out of the 37 smartwatches he tested out.
How Does Apple Watch Sleep Tracking Work?
The Apple Watch tracks various metrics when I sleep, which are:
- Time in bed
- Time asleep
- Awake, REM, core, and deep sleep stages
- Heart rate
- Respiratory rate
- Wrist temperature
But how does it know when I fell asleep and determine the sleep stages
The Apple Watch has various sensors that help the device track a myriad of metrics throughout the day. For determining sleep, it uses its 3-axis accelerometer that captures body movements, such as tossing and turning around in bed, and even smaller movements, such as breathing patterns.
These movements are then analyzed by an algorithm that essentially classifies each 30-second interval into one of four sleep stages.
Now, this algorithm aligns with standard clinical scoring methods because Apple has conducted extensive research in both laboratory and at-home settings involving a diverse population, ensuring inclusivity in areas such as age, race, gender, ethnicity, and sleeping disorders.
What I Found About Apple Watch’s Sleep Tracking:
I’ll start off by saying that no wearable device is completely accurate in detecting sleep and its stages. The same is impacted by external factors such as light and movement. So, be it a smartwatch or a smart ring, I don’t put them on a pedestal just to be disappointed later.
Having said that, the Apple Watch has been pretty spot on with my total time asleep. It does, however, slightly overestimates my time in bed at times. There were also a few days when my Apple Watch calculated longer ‘time asleep’ than ‘time in bed’. Upon research, this is a common occurrence with many users who regularly use their Apple Watch to track their sleep.
The best part is that I can set my sleep schedule, and half an hour before this time, the phone and watch go into sleep focus to help wind down before bed. While in sleep focus, the screen is dim, and my notifications are set to ‘none allowed’ so as not to be so tempted about constantly checking my phone and, in turn, getting better sleep. Coming to the sleep stages, as we have established above, the stages are something that can’t be exactly calculated.
However, a longer REM sleep stage works beautifully for mental clarity and well-being.
Personally, I have found myself to be the most productive, with around 7 hours of sleep. Any more or any less, and I feel groggy, and it hampers my productivity. Therefore, with any wearable I choose, I strive to hit the bed at a certain time and get around 7 hours of sleep.
Additionally, for optimal health, I focus on better sleep habits for an upward HRV graph. Even regular checks of my body temperature and respiratory rate help in identifying potential illnesses.
Why I Won’t Be Wearing My Apple Watch to Sleep:
Although the Apple Watch is one of the top sleep trackers on the market, would I still continue to wear it to bed? Honestly, no. As much as I don’t doubt its capabilities to help me get my sleep on track, I’m gonna stick to a smart ring for this purpose. Here are all the reasons why :
- The battery needs to be charged before bed, especially if I wear my Apple Watch throughout the day.
- The sleep scores on other wearables give me a quick glance at my sleep from the night before without having to dive into the data, a feature missing in the Apple Watch.
- My bedtime doesn’t always align with the schedule I have set for myself, and it affects the data.
- The data on other wearable devices is much more evolved than Apple’s.
- It is not comfortable to sleep with, especially since I can’t fall asleep without keeping my hand under the pillow.
Wrap Up
If anyone has tried to sleep wearing an Apple Wach, or any smartwatch for that matter, you would understand why I stick to a smartring instead. That being said, if you are looking for a smartwatch to track your sleep as well as activity and you’re comfortable wearing a watch to sleep, the Apple Watch makes for a great choice.
