What are the functions of deep sleep?

Deep sleep serves several important functions for the body and brain:

1. Nervous System: Deep sleep shifts the body into a parasympathetic state, promoting calmness and reducing activity in the sympathetic, or "fight or flight" systems. This transition helps send a message to the body to calm down 1.

2. Cardiovascular Health: Deep sleep can be likened to blood pressure medication, as it significantly lowers the cardiovascular system's workload, providing rest and recovery 1.

3. Immune System: It enhances the immune system by restocking the weaponry of our immune arsenal, such as T cells and natural killer cells, so that we are more immune-robust when we wake up 2. This increased armory, paired with a heightened sensitivity to immune signals, makes the body more adept at handling immune challenges 2.

4. Metabolic Regulation: Deep sleep is crucial for controlling blood sugar and metabolic rate. In fact, selective deprivation of deep sleep can impair the body's ability to manage blood sugar levels, demonstrating deep sleep's role in maintaining metabolic health 2.

5. Memory Consolidation: Sleep, notably deep sleep, is essential for memory processing, where the brain cross-links and integrates new memory information with the existing memory network, aiding in creative problem-solving and developing new insights 3.

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6. Emotional Health: It acts as an emotional balm that can soothe emotional stress and wounds. Individuals often feel better the next day after a good night's sleep due to this restorative emotional effect 3.

7. Glymphatic System: Deep sleep is associated with the activation of the glymphatic system, a brain-cleaning process that removes neuroinflammation and clears out debris, supporting recovery from infection and other forms of inflammation 4.

8. Hormone Regulation: Sleep helps regulate stress hormones such as cortisol, keeping its levels in check during the time when high cortisol would be harmful, and aligning its release with the circadian rhythm for optimal function 5.

9. Neuroplasticity: Deep rest and sleep contribute to the process of neuroplasticity, which is critical for learning and unlearning, whether it’s acquiring new skills or reducing the emotional impact of memories 6.

These functions demonstrate the indispensable role that deep sleep plays in overall health, cognitive function, and emotional well-being.

Improving deep sleep involves creating conditions that promote relaxation and support the natural physiological processes associated with sleep. Here are some suggestions from Andrew Huberman:

1. Dimming Lights: Reduce light exposure in the evening to signal to your body that it's time to wind down. Light serves as a wake-up signal, so dimming lights can help prepare you for sleep 1.

2. Non-Sleep Deep Rest (NSDR): Engage in practices like Yoga Nidra, which are designed to teach you to lower activation levels in your nervous system. These practices can be useful if you wake up during the night and have trouble falling back asleep 1.

3. Cold Exposure: Cold showers or baths can increase brown adipose tissue in your body, improving metabolism and resilience. This can be beneficial in terms of total sleep quality and it's recommended to accumulate around 11 minutes of cold exposure per week 2.

4. Room Temperature: Keep your sleeping environment cool, as the body needs to drop in temperature to initiate sleep and remain asleep. Pile on blankets if you’d like to feel warm, but the ambient temperature should be lower 3.

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5. Meal Timing: Experiment with the timing of your last meal before bed. Some suggest a gap of a few hours between your last meal and bedtime, but individual responses vary, so find what works for you 3.

6. Light Exposure at Night: If you wake up during the night, avoid bright lights as they can inhibit the hormone melatonin and make it difficult to go back to sleep. Use minimal lighting if necessary 4.

7. Supplements: Consider supplements that support sleep, such as magnesium threonate or bisglycinate, and theanine, only if behavioral changes do not suffice. Always check with your doctor before taking supplements 3 5.

8. Avoiding Caffeine: Restrict caffeine intake later in the day to improve your ability to get deeper rest and facilitate neural plasticity during sleep 4.

9. Regular Practice: Develop a regular practice of NSDR or Yoga Nidra during the day, which can also be used at night if you wake up. This practice can help with self-directed relaxation 5.

Each of these strategies can contribute to an improvement in your deep sleep quality. Remember to tailor these suggestions to your individual needs and preferences for best results.