How Apple Watch Tracks Sleep

The Apple Watch can be used to track sleep, with the Sleep app showing the amount of sleep the user got the night before, the time spent in each sleep stage, and their sleep average over the last 14 days. The watch can also track the user's respiratory rate, which can be viewed in the Health app on their iPhone or iPad. However, reviews suggest that while Apple's sleep tracking is one of the best among smartwatches, it is not perfect, with some users reporting inaccuracies in the data.

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Apple Watch sleep tracking accuracy

The Apple Watch's sleep tracking feature uses your motion to detect sleep when you wear the watch to bed. It can also track your breathing rate while you sleep, which can give you greater insight into your overall health. To view your respiratory rate, open the Health app on your iPhone or iPad.

Apple Watch's sleep tracking accuracy has been the subject of various discussions and studies. While some users have questioned the accuracy of the Apple Watch's sleep tracking, particularly in detecting deep sleep, others have found it to be one of the most accurate wearable devices for sleep tracking. In various reviews, Apple's sleep tracking data is considered the best among smartwatches. According to some users, the Apple Watch consistently reports lower deep sleep scores than other devices and algorithms. However, it has been noted that no app or watch can accurately measure sleep stages, and they all rely on algorithms to make their best guesses.

A study published in PMC compared the accuracy of 11 different consumer sleep trackers (CSTs), including the Apple Watch 8, and found that the Apple Watch exhibited diverse performances across sleep stages. While it showed high proportional bias in sleep efficiency, it was not as accurate in detecting deep sleep when compared to other devices like the Google Pixel Watch and Fitbit Sense 2.

Another study by The Quantified Scientist, a popular source for science-based information, comparisons, and reviews, analysed the Apple Watch algorithm and rated it as the best wearable for sleep tracking. However, it was noted that the Apple Watch reported lower deep sleep scores than what is considered normal for healthy adults.

To get the most accurate results when using the Apple Watch to track your sleep, it is recommended to have the watch charged to at least 30% before bed and to wear it for at least 1 hour while sleeping. Additionally, you can turn on Charging Reminders to ensure your watch is sufficiently charged before your wind-down time.

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Sleep tracking features

The Apple Watch has various sleep-tracking features, including the ability to track sleep schedules, sleep goals, and respiratory rate. Here is a detailed overview of these features:

Sleep Schedules

Apple Watch users can create personalized sleep schedules to help meet their sleep goals and improve their overall health. This feature allows users to set a bedtime and wake-up time, which can be customized as needed. The watch also provides wind-down reminders, notifying users when it is time to start preparing for bed.

Sleep Goals

Users can set a sleep goal, which is the number of hours of sleep they want to achieve each night. This feature helps users stay focused on their sleep health and can be adjusted as needed.

Sleep Focus

Sleep Focus is a setting that limits distractions before bedtime and protects sleep after the user is in bed. It simplifies the lock screen and reduces notifications, allowing users to wind down and prioritize sleep. Certain people or apps can be given permission to notify the user even during Sleep Focus.

Sleep Tracking

The Apple Watch uses motion detection to track sleep when worn to bed. It measures and records the number of times the wearer breathes in a minute, providing data on their respiratory rate. This feature is available on watchOS 8 or later, and users are prompted to ensure their watch is charged to at least 30% before bed.

Respiratory Rate Tracking

In addition to sleep tracking, the Apple Watch can help monitor the user's breathing rate during sleep. This data is synced with the Health app on the iPhone, providing insights into overall health. It is important to note that respiratory rate measurements are not intended for medical use.

While the Apple Watch's sleep-tracking features offer valuable insights, some users have noted limitations, such as the need to set schedules upfront and the potential for inaccuracies in deep sleep detection. However, Apple has invested extensively in research, and its devices are considered among the most accurate on the market for sleep tracking.

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Sleep tracking compared to third-party apps

The Apple Watch Series 3 and later versions with watchOS 8 or later can measure and track your Respiratory Rate. With Sleep Tracking on Apple Watch enabled, the watch will automatically measure and record the number of times you breathe in a minute when worn to bed. The data is then added to the Health app on your iPhone. The watch also allows you to set up a sleep schedule, a sleep goal, and a bedtime reminder.

Third-party apps such as Sleep Cycle, SleepScore, and Pillow also offer sleep-tracking features. Sleep Cycle uses sound-sensing technology to assess your sleep, using the microphone to detect the sounds you make when you move. SleepScore is known for its specific and easy-to-understand privacy policy, and Pillow was one of the three apps included in a study that compared 11 sleep trackers against PSG.

In 2018, the sleep-tracking features of the Apple Watch were tested against four apps, and the wearables were found to be frequently off compared to the apps, usually over-reporting sleep. However, the Apple Watch did provide an accurate picture of sleep trends over time with consistent use. The biggest advantage of sleep-tracking phone apps over wearables is the extra features, such as smart alarms and sounds that help you fall asleep.

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Charging reminders

The Apple Watch's battery life has been criticised for not being ideal for sleep tracking. However, Apple Watch does provide charging reminders to ensure your device has enough power to track your sleep.

To turn on charging reminders, open the Watch app on your iPhone and tap the My Watch tab. Then, tap Sleep and turn on Charging Reminders. You will then be reminded to charge your watch before your wind-down time and notified when your watch is fully charged.

If your Apple Watch is charged less than 30% before you go to bed, you will be prompted to charge it. It is recommended that you ensure your Apple Watch is charged to at least 30% before bed with Sleep Tracking enabled.

You can also set up a sleep schedule, including a sleep goal (how many hours of sleep you want to get) and a wind-down period before your scheduled bedtime. During the wind-down period, Sleep Focus will be turned on, limiting distractions and protecting your sleep.

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Sleep schedules

The Apple Watch can help you track your sleep schedule and set up sleep goals. To enable sleep tracking, you must ensure your Apple Watch is charged to at least 30% before going to bed. You can set up a sleep schedule with the following general settings:

• A sleep goal (the number of hours of sleep you want to get)
• Whether to turn on Sleep Focus, which limits distractions before you go to bed and protects your sleep after you're in bed
• When to start winding down before bed, which gives you a bedtime reminder and turns on Sleep Focus
• Sleep tracking, which uses your motion to detect sleep when you wear your Apple Watch to bed

You can also create multiple sleep schedules, for example, one for weekdays and another for weekends.

In addition to tracking your sleep schedule, the Apple Watch can also help you track your breathing rate as you sleep, providing greater insight into your overall health. This feature is available for Apple Watch Series 3 or later with watchOS 8 or later.

While the Apple Watch can help you track your sleep schedule, it's important to note that getting enough sleep is just one aspect of maintaining a healthy sleep schedule. Here are some additional tips to improve your sleep habits:

• Maintain a consistent sleep schedule by going to bed and waking up at the same time each day.
• Create a relaxing bedtime routine, such as reading or taking a bath, to help you wind down before sleep.
• Make sure your bedroom is quiet, dark, and at a comfortable temperature.
• Avoid caffeine, alcohol, and heavy meals before bedtime, as they can interfere with your sleep quality.
• Manage stress through relaxation techniques such as guided imagery, listening to music, or practicing yoga or meditation.
• Limit screen time before bed, as the blue light emitted by electronic devices can disrupt your sleep.

If you're considering making significant changes to your sleep schedule, it's important to consult a healthcare professional. Additionally, if you're experiencing insomnia or other sleep disorders, seek professional advice to find the best treatment options.

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