The Basics: Deep Sleep

What is deep sleep?

Deep sleep, scientifically known as slow-wave sleep (SWS), is one of the four sleep stages. Deep sleep typically occurs during the first half of the night and is characterized by its slow brain waves, minimal eye movement, and significant muscle relaxation. 

Deep sleep and your body’s physical repair

During this phase, your body focuses on essential tasks related to physical repair.

1. Tissue Repair and Growth: Deep sleep is your body's prime time for repairing and growing tissue. This includes mending muscle tissue, healing from injuries, and enhancing your immune system's ability to fend off illnesses. For athletes and fitness enthusiasts, deep sleep is like the body's remodeling phase, where it rebuilds and strengthens muscles after the wear and tear of a vigorous workout.

2. Hormone Release: Another significant aspect of deep sleep is the release of growth hormones, such as human growth hormone (HGH). These hormones play a pivotal role in tissue repair, muscle development, and overall growth. HGH, in particular, is crucial for maintaining a youthful appearance and promoting muscle strength.

3. Energy Restoration: During deep sleep, your body recharges its energy reserves. As you progress through this phase, your body replenishes the energy you've expended throughout the day, ensuring you wake up feeling refreshed and ready to tackle the challenges that await you.

How to interpret your deep sleep data

Interpreting your deep sleep data can provide valuable insights into your sleep quality. While Bevel uses deep sleep as an input for Sleep Score, here's what you should keep an eye on when looking at deep sleep in isolation:

Duration of Deep Sleep: This is the amount of time your device estimates you spent in Deep Sleep. Interpret it alongside your age, longer-term patterns, and how you feel during the day. More Deep Sleep is not automatically better, and a single night’s estimate does not establish whether your sleep is healthy or unhealthy.

Proportion of Deep Sleep: The percentage shown in your sleep breakdown describes how much of your recorded sleep was Deep Sleep. Bevel’s scoring target, however, is calculated using Sleep Needed and adjusts for age and biological sex when available. Across ages 30 to 70+, the target decreases from 13% to 9% of Sleep Needed for males and from 14% to 10% for females. These are Bevel’s scoring targets, not clinical minimum requirements.

Consistency: Look for patterns in your deep sleep data over time. Is there a consistent trend, or does it vary significantly from night to night? Consistency is key for restorative sleep.

Daytime Functionality: Assess how you feel during the day. If you're consistently getting a healthy amount of deep sleep, you should wake up feeling refreshed, alert, and physically recovered.

How to improve deep sleep

Now that you understand the importance of deep sleep, here are some practical tips to help you get more of it:

1. Stick to a Consistent Schedule: Your body's internal clock thrives on routine. Aim to go to bed and wake up at the same time each day, even on weekends. This helps regulate your sleep cycles, making it easier to achieve deep sleep.

2. Create a Relaxing Bedtime Routine: Wind down before bedtime with activities that relax you, such as reading, gentle stretching, or a warm bath. You can also engage in techniques such as meditation, deep breathing, or progressive muscle relaxation to ease your mind before bedtime.

3. Optimize Your Sleep Environment: Ensure your bedroom is conducive to sleep. Keep the room dark, cool, and quiet. Consider using a white noise machine or earplugs if needed.

4. Limit Exposure to Blue Light: The blue light emitted from electronic devices can disrupt your circadian rhythm and inhibit deep sleep. Try to avoid screens at least an hour before bedtime, or use blue light filters.

5. Stay Active: Regular physical activity during the day can promote deeper and more restful sleep. However, avoid intense exercise close to bedtime, as it can be stimulating.