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Why should you go to bed between 10pm and 11pm?

Staying up late is almost synonymous with staying up all night, but how late is considered staying up all night? Traditional Chinese Medicine (TCM) believes that falling asleep after 11pm is considered staying up all night. Adults are best to go to bed before 10pm, while children are recommended to go to bed before 9pm.

TCM has found that 11pm to 3am is the period when the qi and blood of the gallbladder and liver zang-fu organs are most vigorous, especially the liver, which is responsible for the allocation and storage of energy and resources in the body. Modern medicine has also discovered that the liver, in addition to storing a large amount of "essential resources," is also the body's main chemical factory, responsible for the metabolism of most substances in the body, removing toxins (converting toxic substances into non-toxic ones). Sleeping at the right time allows the liver to fully perform its function of removing toxins, so this period can be considered the body's detoxification period. Missing this period of rest can lead to the retention and accumulation of toxic metabolic waste in the body, harming the body.

According to modern medical findings, the secretion of melatonin, which aids human sleep, is most vigorous between 11pm and 2am; the secretion of growth hormone, which aids tissue repair, is most vigorous between 1am and 2am. These endocrine secretions fall under the category of "kidney qi" in TCM.

A European study ⁽¹⁾ found that the timing of falling asleep is also related to the risk of heart disease: compared to those who sleep between 10pm and 11pm, those who sleep between 11pm and 12am have a 12% higher risk of cardiovascular disease, those who sleep after 12am have a 25% higher risk, and those who sleep before 10pm have a 24% higher risk of cardiovascular disease.

The relationship between sleep and melatonin

Melatonin is secreted by the pineal gland in the brain, inhibited by light, and is almost entirely secreted at night, peaking between 11pm and 2am, and stops secreting as soon as one opens their eyes in the morning. Generally, secretion is highest at age 6, begins to decrease during adolescence, and by around age 45, the secretion is only half that of childhood.

The effects of melatonin are as follows:

• The secretion of melatonin is very regular, and insufficient sleep or disruption of the physiological cycle can significantly reduce its secretion. Just one night of staying up late can reduce the secretion the next day, and it takes about 11 days to recover. If the regularity of melatonin secretion is disrupted, symptoms such as insomnia, lack of energy, and daytime drowsiness may occur.
• Melatonin can inhibit the sympathetic nervous system, slowing the heart rate, lowering blood pressure, and relaxing muscles, enhancing the immune system and killing cancer cells.
• Researchers at the University of Virginia found that mice with disrupted biological clocks die earlier, leading them to believe that shift work causing day-night reversal or frequent flying across different time zones may have negative effects on health. Studies have shown that women who frequently work night shifts have a 2-fold increased incidence of breast carcinoma.
• According to research, people who sleep with the lights on at night may experience a decline in immune function and are more prone to cancer.

The Relationship Between Sleep and Growth Hormone

Not only do children need growth hormone to promote growth and development, but adult tissues also require an appropriate amount of growth hormone stimulation to maintain normal functioning. Infants secrete growth hormone throughout the day; starting from childhood, the usual secretion of growth hormone decreases, with secretion peaks occurring only after deep sleep; in adults, the concentration is significantly highest at 1-2 am, and almost zero at other times.

• Children who stay up late don't grow tall: A Minnan proverb says, "Sleep soundly, grow an inch each night." Height is related to factors such as genetics, nutrition, and exercise, but it is also determined by the stimulation of growth hormone.
• Staying up late can weaken the body: For adults who have stopped growing, the peak secretion of growth hormone that occurs after deep sleep is still beneficial for promoting physical recovery. Growth hormone promotes protein synthesis and cell repair, including skin cells. If one stays up late, insufficient growth hormone secretion prevents effective cell renewal, leading to dull skin and poor overall health. After the age of 50, the peak secretion of growth hormone disappears, and the decline in physical strength may also be related to this.
• Some studies suggest that night owls have a similar total daily secretion of growth hormone compared to those with normal sleep patterns, but they experience two peaks: one during the typical sleep period and another after they sleep. Although the total secretion is similar, the effectiveness remains to be studied.

Growth hormone is not always better in larger amounts. Excessive growth hormone in adolescents can lead to gigantism, and in adults, it can cause acromegaly. It can also excessively inhibit the activity of 1α-hydroxylase in the kidneys, leading to long-term vitamin D deficiency, reduced calcium absorption in the intestines, and contributing to osteoporosis. Balance is key in all things.

How much sleep is enough?

According to the National Sleep Foundation in the United States, teenagers aged 14-17 need an average of 8-10 hours of sleep, while adults need 7-9 hours.

A sleep study by Seoul National University College of Medicine: 13,164 participants were divided into groups based on their daily sleep duration (less than 5 hours, 6 hours, 7 hours, 8 hours, and more than 10 hours). After 17 years of follow-up, the differences in mortality rates were observed. Results: Compared to the baseline of 7-8 hours of sleep, those who slept less than 5 hours had a 21% higher mortality rate, and those who slept more than 10 hours had a 36% higher mortality rate. ⁽²⁾

A sleep study by the Stress Research Institute at Stockholm University, Sweden: Over 13 years, the sleep, disease, and mortality data of more than 43,000 people were tracked. Participants were divided into three groups: short sleepers (less than 5 hours), medium sleepers (around 7 hours), and long sleepers (more than 9 hours). Results: Compared to medium sleepers, short sleepers had a 52% higher mortality rate, and long sleepers had a 25% higher mortality rate. Notably, those who slept 5 hours on weekdays and 7-8 hours on weekends had a mortality rate similar to medium sleepers, leading the authors to conclude that catching up on sleep during weekends can help avoid a shorter lifespan. ⁽³⁾

A nearly 30-year study from the Pennsylvania State University College of Medicine found that individuals with hypertension or diabetes who sleep less than 6 hours per night have twice the risk of dying from heart disease or apoplexy compared to those who sleep more than 6 hours. Additionally, those who sleep less and already suffer from heart disease or apoplexy have a threefold increased risk of dying from cancer. ⁽⁴⁾

So, sleeping 7-8 hours is just right; sleeping too little or too much can lead to early death and exacerbate existing illnesses.

What harm does staying up late and pulling all-nighters do to the human body?

After staying up late, the damage that individuals can intuitively feel and observe is as follows:

• Skin becomes rough: The skin is one of the areas in the human body where cell metabolism and division are most vigorous. If you don't sleep well, the metabolic waste accumulated in the skin is not completely cleared, injuries are not fully repaired, and the supplies and energy needed for the next day are also insufficiently stored. The skin does not get enough nutrition, and the skin quality naturally deteriorates. Modern medicine believes that staying up late can greatly increase the secretion of adrenaline, increase sebum secretion, clog pores, causing acne, rough skin, and enlarged pores.
• Causes erectile dysfunction in men: Long-term sleep deprivation leads to a depletion of vital essence and blood, naturally making it difficult for men to achieve an erection, and even if they do, it is not strong. This is the body's self-protection mechanism, urging the owner not to deplete the body's important resources further. If drugs are taken to achieve an erection and intercourse is forced, it is like borrowing from a loan shark, further depleting the already deficient vital essence and blood, leading to self-destruction.
• Leads to weight gain: Research has found that frequent late nights can lead to weight gain. Because staying up late keeps the body in a state of alert (i.e., the stress state in modern medicine), the body increases its defense index and naturally accumulates more calories to prepare for stress needs, hence gaining weight. Also, staying up late leaves the body no time to clear metabolic waste, and the long-term accumulation of metabolic waste is also a cause of weight gain, but this is a bloated weight.
• Causes various symptoms of "heatiness" (上火): Such as dry mouth, bitter mouth, mouth sores, bloodshot eyes, dry eyes, tinnitus, severe acne, dark yellow urine, constipation, etc.
• Easily fatigued: Feeling listless during the day, sore back, feeling like collapsing from slight overexertion, or starting to feel drowsy by evening near the end of work, and the onset or worsening of chronic diseases, etc.
• As age increases, the side effects of staying up late become more pronounced.

A study from the State University of New York pointed out that insufficient sleep not only causes cardiovascular diseases, diabetes, obesity, or a decrease in quality of life but also interferes with the body's "bone remodeling" process, increasing the risk of osteoporosis and fractures. The study surveyed more than ten thousand postmenopausal women and found that those who slept only 5 hours had a bone age equivalent to one year older, with increases in osteoporosis risk at the hip, neck, and spine by 63%, 30%, and 28% respectively, and a 94% increase in overall osteoporosis risk. ⁽⁵⁾

In summary, staying up late causes comprehensive harm to the human body. What most people notice are the superficial damages, but consider this: if the skin becomes rough due to lack of sleep, wouldn't the internal tissues, organs, five zang and six fu-organs also become "rough"? If men can experience erectile dysfunction, wouldn't women also lose their "sexual interest"? Gaining weight indicates the accumulation of useless substances and metabolic waste in the body, doesn't it? If children don't grow tall, doesn't it mean that cell growth and tissue repair inside the body are affected? Therefore, the harm of staying up late is comprehensive. Young people or those with a good constitution might tolerate short-term sleep deprivation, but the damage is latent and cumulative; for older individuals, the damage can be immediately apparent.

Is it useful to catch up on sleep after staying up late?

According to a sleep study in the United States, catching up on sleep after staying up late cannot completely mitigate the cognitive damage caused by sleep deprivation⁽⁶⁾; another sleep study shows that catching up on sleep has little effect on metabolic issues caused by sleep deprivation (such as weight gain, reduced insulin sensitivity, etc.)⁽⁷⁾.

The harm of long-term sleep deprivation

One of the profound effects of long-term sleep deprivation and staying up late on the body is the depletion of your "essence" and "blood," turning you into a constitution that is easily fatigued, followed by a host of minor ailments, and eventually leading to various diseases. How so? This requires an understanding of what "essence" and "blood" mean in TCM.

The various nutrients in the human body are the foundation for generating energy and building tissues. TCM succinctly categorizes these substances into the broad concepts of "blood" and "essence."

The "blood" in TCM is different from the blood in modern medicine. Broadly speaking, "blood" refers to a group of nutrients (including oxygen, glucose, amino acids, fats, etc., in modern medicine) required for daily consumption by the body. After food is digested and absorbed by the stomach and intestines, it is transformed into "blood," which is then transported through the blood vessels to the entire body to meet daily needs. Any excess "blood" is stored in the liver system (which is not entirely equivalent to the liver in modern medicine) as a reserve "storage blood," to be used when there is no food or during times of high demand (such as intense exercise, emergencies, staying up late, common colds, etc.).

The "essence" in TCM does not specifically refer to semen discharged from the reproductive organs. Broadly speaking, "essence" refers to the most refined group of substances in the human body, used for tissue repair, reproduction, and the growth and development of children. Its formation is slower and its uses more fundamental than "blood," making it more important. After food is digested and absorbed by the stomach and intestines, the most refined part becomes "essence" (including amino acids, nucleic acids, vitamins, minerals, trace elements, etc., in modern medicine). Beyond daily needs, the excess is stored in the deeper kidney system (which is not entirely equivalent to the kidneys in modern medicine) as a reserve "storage essence," to be used when there is no food or during times of high demand (such as tissue repair, intense studying, gamete production, etc.).

Most people have experienced this: when studying or working late, one gradually feels drowsy, but once they push through this drowsy period, they suddenly feel a surge of energy and mental clarity, allowing them to continue. At this point, the body has switched to a reserve mode, known as the "stress response" in modern medicine. Activating the stress response causes the body to start burning reserves that are usually kept unused. This unusual mode of operation generates more metabolic waste than usual, and the body has to expend several times more effort to clean up afterward. This is one reason why people feel lethargic, have poor skin, and look haggard the day after staying up late.

Long-term late nights and staying up late can keep the body frequently in a reserve mode, where the reserve "essence" and "blood" are often used, leading to more output than input. Over time, this inevitably leads to depletion, resulting in a constitution that cannot handle stress, making it difficult to stay up late or work long hours, easily fatigued, prone to common colds, and plagued by minor ailments.

Once essence and blood are depleted, they cannot be replenished in a short time. The medical sage Sun Si-miao mentioned in Beiji Qianjin Yaofang that those with depleted blood need three years of rest and normal living, avoiding overly stimulating activities, to recover. Naturally, replenishing essence takes even longer.

Another adverse effect of frequently entering the reserve mode is that the brain becomes easily alert, making it difficult to fall asleep at night, waking up too early in the morning, or being easily startled by minor disturbances, leading to an insomnia constitution. Alternatively, one may feel sleepy during the day and more energetic at night, resulting in a yin-yang inversion constitution. In modern medicine, this is considered a type of autonomic nervous system disorder: the sympathetic nervous system should be more active during the day, and the parasympathetic nervous system should be more active at night. For patients with yin-yang inversion, the opposite is true. If such patients do not improve their sleep habits, their condition cannot be cured.

Chronic sleep deprivation may also plant the seeds for dementia in the long run. According to research, individuals with poor sleep quality and frequent awakenings have more β-amyloid plaques deposited in their brains, leading to brain cell apoptosis, reduced gray matter volume, and the onset of Alzheimer's symptoms. ⁽⁸⁾

Of course, there are constants and variables. The above discusses the constants. There are also exceptions like owls, which are active at night and rest during the day without issues, but these are extremely rare. If your constitution does not belong to this type, do not pretend to be an owl and ruin your health.

Rest is for walking a longer road

Why does just staying up late or pulling all-nighters cause such significant harm? The so-called "cultivation and rest" means that only through cultivation can one truly rest. If a bank's deposits are frequently moved, how much interest can be accumulated by the end of the year? "Rest is for walking a longer road." Can anyone work and rest at the same time? Can a society thrive with ethnic conflicts while all industries prosper? Can a country engage in civil war while simultaneously carrying out infrastructure construction?

The same principle applies to the human body. For example, American scholars have found that during deep sleep, the brain activates a high-speed garbage-cleaning mode, expelling 10 to 20 times more waste than usual. The volume of glial cells in the brain shrinks by 60%, creating more space for cerebrospinal fluid to remove waste.

TCM emphasizes the concept of "correspondence between nature and human": what phenomena exist in nature, similar phenomena exist in the human body. Humans are the microcosm of heaven and earth, the proud children of nature. Daytime is active, governing growth and development; nighttime is passive, governing collection and storage. All things in nature flourish during the day and rest at night. Humans work during the day, consuming many resources and energy, accumulating metabolic waste, and causing minor injuries in tissues. At night, the body prepares to shut down; during sleep, the body begins to clear the metabolic waste accumulated during the day, repair injuries, and store the resources and energy needed for the next day. Upon waking in the morning, one is full of energy and vitality.

Living beings are born within the boundaries of heaven and earth, and these boundaries are the conditions of life. The physical and physiological activities within living beings are naturally constrained by the circadian rhythm, synchronized with nature. As the saying goes, "Those who follow nature prosper, those who defy it perish."

Summary

In short, you only need to grasp one principle: sleep is for eliminating today's fatigue, repairing tissue damage, storing what is needed for tomorrow, and organizing what was learned today. If sleep is disrupted, today's metabolic waste and tissue injuries cannot be fully eliminated, the resources and energy needed for tomorrow cannot be prepared, and what was learned will be forgotten immediately. The person will continue to decline in exhaustion.

Incidentally, poor sleep and insomnia are due to the imbalance of the five zang and six fu-organs. The brain is just the first victim. Do not take sleeping pills, as they only anesthetize the brain nerves, whitewash the situation, and deceive oneself. Long-term use of sleeping pills will lead to mental and nervous breakdowns, complete depletion of vital energy and blood, and weakness of the five zang and six fu-organs, resulting in various illnesses. Just find a good TCM practitioner to balance the functions of your five zang and six fu-organs, combined with proper diet and routine, and you will naturally recover.

bubble_chart Footnote

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