More Sleep Related Knowledge

Why is My Sleep Data Empty?

If you haven't enabled sleep tracking on your Apple Watch or used a third-party app that can write sleep stage data to Apple Health (common apps like AutoSleep do not support writing sleep stages to Apple Health), your sleep quality data will likely be empty.

You can enable sleep tracking on your Apple Watch or use a third-party app like Pillow that writes sleep stage data to Apple Health.

How to Enable Sleep Tracking on Apple Watch?

To track your sleep with an Apple Watch, make sure to meet the following requirements:

  • iOS 16 and above, watchOS 9 and above
  • In the iPhone's Watch app, turn on "Track Sleep with Apple Watch."
  • Ensure your watch is in sleep mode while sleeping.
  • The watch should be unlocked and have sufficient battery.
  • Sleep mode should be enabled for at least 4 hours.

For more details, you can refer to the official Apple documentation: Apple Support for Watch

When Should I Adjust My Sleep Data Source?

Version 2.0.9 and above of StressWatch supports reading sleep data from the Apple Watch, iPhone, and third-party apps.

By default, StressWatch retrieves sleep data in the following order:

  1. Apple Watch
  2. Third-party apps
  3. iPhone's Bedtime

If you find that the data from your Apple Watch doesn't accurately reflect your actual sleep, you can manually adjust the priority of the data source.

Please note, we recommend prioritizing data sources that record both "sleep duration" and "sleep stages" for a comprehensive assessment. If your preferred data source only supports "sleep duration," you won't see an evaluation of sleep quality based on sleep stages.

Why is There a Discrepancy Between StressWatch and Apple Health Sleep Data?

Please note that the sleep data in Apple Health is also influenced by its data source priority settings. To adjust these settings:

  1. Go to Apple Health - Browse - Sleep - Data Sources & Access
  2. Scroll down to Data Sources, then tap the 'Edit' button in the top right corner.
  3. Enable and adjust the specific sleep data priorities to align with those of StressWatch.

This will help ensure that the data displayed in Apple Health and StressWatch are consistent. Note that due to data access and rounding issues, there might be a minor difference in minutes, which is normal.

How to View HRV During Sleep?

HRV during sleep is significantly influenced by sleep stages, especially during the Rapid Eye Movement (REM) sleep cycle, where HRV may fluctuate widely.

Ideally, monitoring HRV throughout the night can help us assess the body's recovery level effectively, but this requires continuous measurement throughout the night.

Since the Apple Watch's default monitoring frequency is relatively low, sporadic data points are not very suitable for nighttime monitoring.

Therefore, if there's an occasional stress overload during nighttime sleep, it shouldn't be a concern.

Instead of nighttime measurements, we recommend observing the overall heart rate changes throughout the night and performing manual HRV measurements upon waking. This can effectively measure our recovery state.

What Do the Sleep Stages Mean?

Each sleep stage plays a different role, but all are crucial for waking up feeling energized.

  • Awake Time: Falling asleep takes time, and we periodically wake up throughout the night, often without realizing it. This time will be shown as "Awake Time" in charts.
  • Rapid Eye Movement Sleep: Research shows that REM sleep may play a key role in memory and becoming alert. This stage is when most dreaming occurs. The eyes move back and forth. REM sleep first appears about 90 minutes after falling asleep.
  • Light Sleep: During this stage, muscle activity slows down, and body temperature drops. Light sleep accounts for most of your sleep time. Though sometimes referred to as light sleep, it is just as important as any other stage.
  • Deep Sleep: Also known as slow-wave sleep, this stage allows the body to repair itself and release key hormones. It occurs in the first half of the night and lasts longer. Because you are very relaxed, it is often hard to wake up from deep sleep.

Among these, REM sleep and deep sleep are the restorative sleep stages of our body, which need special attention.

How to Improve Sleep Quality?

Here are some suggestions:

  1. Maintain a Regular Sleep Schedule

    • Try to go to bed and wake up at the same time every day, even on weekends or holidays. This helps regulate your body clock and promotes faster and deeper sleep.

  2. Create a Comfortable Sleep Environment

    • Ensure your bedroom is quiet, dark, and at a comfortable temperature. Using blackout curtains, earplugs, or white noise machines can help block out noise and light.
    • Controlling temperature at bedtime, keeping limbs cool can make it easier to fall asleep.
    • Choose a comfortable mattress and pillow, as well as appropriate bedding.

  3. Limit the Use of Electronic Devices at Night

    • The blue light emitted by screens can disrupt your biological clock, making it harder to fall asleep. Avoid using phones, computers, and TVs at least an hour before bedtime.

  4. Avoid Caffeine and Alcohol

    • Caffeine and alcohol can interfere with the sleep process, especially if consumed a few hours before bed. Try to minimize caffeine and alcohol intake in the evening.

  5. Maintain a Healthy Diet

    • Avoid eating large meals before bed, especially greasy or heavy foods, which can cause discomfort and affect sleep.

  6. Engage in Regular Physical Activity

    • Regular exercise can help you fall asleep faster and deepen your sleep, but avoid intense workouts right before bedtime.

  7. Establish a Relaxing Bedtime Routine

    • Activities like deep breathing, yoga, meditation, or a warm bath can help relax your body and mind, making it easier to fall asleep.

  8. Manage Stress and Anxiety

    • Learn stress management techniques to reduce the impact of stress on sleep.

Additionally, we recommend pop science reads like "Why We Sleep" and "The Sleep Revolution," where you can discover more sleep tips.