On average, a person spends 1/3 of their life sleeping. Without quality sleep or deep sleep, vital functions of the body cannot occur, leading to serious impacts on health.
1. The role of sleep
Sleep is one of the essential activities crucial for human survival. Sleep is significant for regeneration and recovery, helping to relieve stress and enhance thinking and memory capacity.
Two factors that affect sleep quality are duration and depth of sleep. Sleep is considered high quality when you sleep deep enough and long enough to allow for recovery and regeneration.
Stages of sleep
Typically, sleep consists of 3 to 6 cycles, with each cycle containing 5 stages.
- Sleep onset stage (NREM 1): The first non-rapid eye movement stage, accounting for 2-5% of total sleep time (about 10 minutes). This is the stage when you begin to fall asleep, but it is easy to be awakened.
- Light, deep, and very deep sleep stages (NREM 2, 3, and 4): These stages account for nearly 80% of total sleep time. Heart rate tends to decrease, and body temperature also gradually reduces.
- Dreaming stage (REM): The rapid eye movement stage, where dreaming occurs, and the body releases hormones that temporarily paralyze the limbs. This stage usually accounts for 20% of total sleep time.
After each cycle ends, the body takes us back to NREM 1 to start a new cycle lasting about 90-120 minutes. The ideal number of cycles for optimal sleep is between 4-6 cycles and occurs without interruption.
2. What is deep sleep?
During sleep, your body undergoes many changes, among which deep and very deep sleep occurs in stages NREM 3 and 4. At this point, your eyes will not move much, brain waves occur very slowly and are called delta waves, while body temperature, heart rate, breathing rate, and blood pressure all decrease. The musculoskeletal system also relaxes, allowing the body to rest almost completely.
If someone wakes you up, you will feel disoriented for a few minutes. It takes several minutes for the brain to function normally again.
How long is deep sleep enough?
During the deep sleep stage, many activities still take place in the body and mind, including:
- Storing and reorganizing memories in the brain.
- Engaging in learning and emotional processing.
- Recovering and regenerating the body.
- Promoting metabolic processes and balancing blood sugar.
- Boosting the immune system.
- Detoxifying the brain.
For healthy adults, deep sleep accounts for about 13-23% of total sleep. Therefore, if you sleep a full 8 hours, the deep sleep duration should be around 60-120 minutes. However, this also depends on age; the older you get, the harder it becomes to achieve deep sleep.
3. The effects of sleep deprivation
Similar to food and water, the quality of sleep is crucial for health and helps humans survive and develop. Some side effects of sleep deprivation and poor-quality sleep include:
- Hormonal imbalance, obesity: when sleep is lacking, the body releases a large amount of the hormone Ghrelin, causing increased appetite, combined with fatigue, leading to weight gain.
- Weakened immune system: internal bleeding, allergies, stomach bleeding. Sleeping less than 6 hours a day or experiencing shallow, frequently interrupted sleep increases the risk of death due to high blood pressure, cardiovascular diseases by 46%, and increases the likelihood of stroke by 15%.
- Decline in memory, lack of concentration, difficulty controlling emotions: leading to a decrease in quality of life and work.
- Poor balance, increased risk of accidents. Sleep deprivation and insufficient sleep cause the brain to enter a state similar to intoxication, leading to distraction and a higher risk of accidents affecting others.
4. Tips for a good night’s sleep
Choose the right time to sleep
The human body regenerates and recovers most effectively when sleep is in sync with the hormone cycle. Specifically, between 10 PM and midnight, the body releases a large amount of Melatonin, helping to restore the immune system, repair free radicals, aid in weight loss, and limit the growth of cancer cells.
Therefore, depending on the different times of the year, you should limit yourself to about 9 PM to midnight so that your sleep can synchronize more effectively with the hormone cycle.
Do not use electronic devices 90 minutes before going to sleep.
Using electronic devices before sleep causes the body to secrete less Melatonin and more Cortisol, leading to stress and disrupting the natural sleep cycle. Therefore, instead of using electronic devices, you should read books or chat with others to allow your brain to completely relax and feel comfortable. This is the most effective method to improve the quality of sleep for everyone after just 1 or 2 days of application.
4-Hour Deep Sleep Method:
- Step 1: Lie on your back on the bed, relax the muscles in your face (tongue, jaw, muscles around the eyes, and relax the eye sockets).
- Step 2: Lower your shoulders as much as possible (to help the shoulders stretch out and reduce pressure on the neck area). Relax the upper and lower half of one arm, then do the same for the other arm. Do the same for both hands and fingers.
- Step 3: Exhale and relax your chest, then inhale until your lungs are full of air.
- Step 4: Relax your legs, relieve pressure from both thighs, then relax your calves and finally focus on relaxing your feet and ankles.
- Step 5: Clear your mind with the following visualization: imagine you are relaxing by a tranquil lake, with a clear blue sky above your head. Or imagine you are curled up in a soft velvet hammock in a completely dark room.
On average, a healthy adult has about 1-2 hours of deep sleep in 8 hours of sleep each night. There are many ways to assess sleep quality, from personal tracking to sleep studies. However, if you notice signs of waking up tired, sluggish, or not getting deep sleep, you should consult a doctor or seek healthcare services for further advice and diagnosis.
