Deep sleep, also known as slow-wave sleep, is a unique stage of sleep, which is characterized by slow brain waves and is considered to be a restorative period for the body. It plays a critical role in everybody's health and recovery. 

In the architecture of sleep, slow-wave sleep is difficult to arouse people out of, while REM sleep is considered very deep sleep due to the vivid dreams and difficulty awakening someone from it. However, the term "deep sleep" typically refers to slow-wave sleep because of the challenge of arousing someone from this state and their likely confused state if awakened.

How does deep sleep work?

Deep sleep, also known as slow-wave sleep or non-REM sleep, involves a few key processes in the brain and body that are critical for rest and recovery.

The transition between alertness, rest, and deep sleep states is managed by the autonomic nervous system, composed of two primary parts: the alertness system (sympathetic nervous system) and the calmness system (parasympathetic nervous system). As evening arrives, our bodies transition from a state of alertness to one of calmness, which leads to sleepiness and, eventually, sleep. This transition is vital for enabling our nervous system to engage in neuroplasticity, the ability of our brain to change and adapt.

The brain's electrical activity slows down during deep sleep, and we experience large, slow brain waves. This sleep phase is crucial for physical rejuvenation, consolidation of new memories, and overall cognitive health. During deep sleep, the body performs necessary repairs and muscle growth and releases hormones that contribute to growth and appetite regulation.

Why do we need deep sleep?

Deep sleep, also known as slow-wave sleep, offers numerous benefits for both the body and mind. Some of the key advantages of deep sleep include:

• Learning and Memory Consolidation: Deep sleep enhances neuroplasticity, helping the brain to consolidate and retain new information and skills by helping to transfer new knowledge from the hippocampus to the neocortex.

• Physical Restoration: During deep sleep, the body repairs tissues, leading to physical restoration, muscle growth, and immune system strengthening.

• Hormonal Balance: Deep sleep is essential for the secretion of hormones like human growth hormone, which is vital for growth and development.

• Immune System Support: It helps make our immune system stronger and promote overall health and well-being.

• Toxin Clearance: Research suggests that deep sleep may aid in clearing out toxins from the brain, with the potential to reduce the risk of conditions like dementia and Alzheimer's disease.

• Metabolism Regulation: Adequate quality sleep is crucial for regulating metabolism, including sugar metabolism, which is linked to appetite control and may have implications for obesity and type 2 diabetes.

How much deep sleep do you need?

The amount of deep sleep needed varies from person to person and can change from night to night. Most adults spend about 10% to 25% of their total sleep time in deep sleep, translating to approximately 48 minutes to two hours if you need eight hours of sleep.

While there are no definitive guidelines for the exact amount of deep sleep required, ensuring you get enough total sleep time is crucial for allowing your brain to self-optimize and spend the proper amount of hours in a deep sleep each night.

Factors like age, overall health, and individual sleep must play a role in determining the ideal amount of deep sleep for each person. It's essential to focus on getting enough total sleep time and maintaining good sleep hygiene practices to support the body's natural ability to cycle through different stages of sleep, including slow-we sleep.

How can you get more deep sleep?

Unfortunately, there are no specific recommendations precisely for deep sleep, but you can there are several strategies and practices to improve the overall sleep quality:

• Non-Sleep Deep Rest (NSDR) or Yoga Nidra: Practicing NSDR or yoga nidra can enhance relaxation during the daytime and can also be used in the middle of the night if you wake up. Many people find these practices help them fall asleep if they are woken up at night.

• Limit Fluids Before Bed: To avoid waking up in the middle of the night, try to limit the total amount of fluids you drink in the last couple of hours before sleep.

• Eating Schedule: Ensure that you do not go to bed with a full belly and adjust your eating schedule so that you don't wake up hungry.

• Supplement Intake: Theanine from tea or supplements can help some people with sleep, and certain supplements like magnesium threonate or magnesium bis-glycinate are also suggested. However, as with any supplement, consult with your doctor before use and follow recommended dosages.

• Temperature Control: Keep the sleeping environment cool. The body needs to drop by about 1 to 3 degrees to get into and stay asleep. You can use blankets as needed, but the environment should be cool.

• Light Exposure: Limit your exposure to light in the evening. Dim lights and using red lights can help to shift your circadian rhythm and improve your sleep quality.

How does age impact deep sleep?

Age significantly impacts deep sleep quality, with older individuals experiencing a decrease in the duration and quality of deep sleep compared to younger adults.

• Decreased Deep Sleep: As individuals age, the amount of time spent in deep sleep decreases. While those under 30 may get around two hours of deep sleep per night, individuals over 65 may only experience half an hour or even none at all.

• Hormonal Changes: Aging leads to lower levels of growth hormone production, resulting in a reduction in slow-wave or deep sleep. This decline in growth hormone and melatonin production can lead to more fragmented sleep patterns and increased awakenings during the night.

• Sleep Disorders: Age-related changes can contribute to various sleep disorders that affect deep sleep, such as insomnia, restless legs syndrome (RLS), and sleep-disordered breathing like snoring and sleep apnea.

• Impact on Health: Poor deep sleep quality due to aging can have significant implications for overall health. It may contribute to conditions like heart disease, Alzheimer's disease, depression, attention problems, excessive sleepiness during the day, and an increased risk of cardiovascular disease and diabetes.

How to track deep sleep hours?

To track your deep sleep hours, you can use various methods and devices like smartwatches, sleep trackers, and sleep apps. Here are some ways to track your deep sleep hours:

1. Apple Watch: You can track your sleep with the Sleep app on Apple Watch, which estimates the time spent in each sleep stage, including deep sleep. The app provides insights into your sleep patterns and trends over time.

2. Sleep Trackers: Devices like the Oura Ring, Fitbit, Apple Watch, Garmin, and Samsung offer sleep tracking capabilities that monitor your sleep stages, including deep sleep. These devices use sensors to detect movement and heart rate variability to estimate different sleep cycles.

3. Sleep Apps: Apps like SleepScore, Sleep Cycle, and Sleep Time use your phone's accelerometer or sonar waves to detect movement during sleep. They provide data on your sleep duration, movement patterns, and different sleep stages, including deep sleep.

4. Smart Mattresses or Sensors: For a more comprehensive approach, you can consider using smart mattresses or dedicated sleep sensors like iFit Sleep HR or Eight Sleep Tracker. These devices track movement, heart rate, and respiratory rates to analyze your sleep cycles and time spent in each stage of sleep.

Utilizing these tools and devices allows you to effectively monitor your deep sleep hours and gain valuable insights into your overall sleep quality. Tracking your deep sleep can help you make informed decisions to improve your sleep hygiene and optimize your restorative rest.