What Traditional Chinese Medicine Thinks about Sleep Cycle and Ideal Bedtime

If you identify with the phrase ‘No rest for the wicked’ in relation to sleeping, chances are, you’re lacking quality snooze time and your sleep cycle is messed up. 

When we doze off, our brain goes through a sleep cycle every night. After you experience drowsiness, your body goes into N1 (light sleep), N2, N3 (deep sleep) and Rapid Eye Movement (REM) sleep. In total, the whole cycle lasts approximately 90 minutes and normally repeats four to six times. Our sleep cycle can also determine how rested we are at night. If we get awakened from our slumber suddenly, the cycle will be broken, and it will have to start all over again. This can decrease our sleep quality and make us feel tired the next day.

The concept of the sleep cycle explained above is based on the 2007 guidelines of the American Academy of Sleep Medicine (AASM). However, Traditional Chinese Medicine (TCM) sees it differently. By looking at what happens in our body every hour while being asleep—and awake, TCM’s version of the sleep cycle may give us an idea about the best time to go to bed. Keep reading to know more! 

Sleeping and the Sleep Cycle in TCM 

To understand the sleep mechanism from TCM’s point of view, we must first go back to one of its foundations, the Yin and Yang principle. With yin representing passivity (descending motion) and yang symbolising activity (ascent), the two forces might be complete opposites, but they are also complimentary. TCM uses yin–yang to interpret many of its theories on health or various diseases and conditions, including sleep.

The ancient Chinese medical text, Lingshu (灵枢), describes how yin and yang influence sleep. In TCM, the sleep-and-awake cycle is regulated by the continuous circulation of wei qi (卫气 , protective qi). It is believed that wei qi travels in yang by day and in yin at night. When yang is depleting, yin will be in fullness, leading to sleepiness. And vice versa; when yin is at its end, yang will be abundant, resulting in wakefulness. 

This process can also explain insomnia and its remedies. TCM views insomnia as the consequence of an excess of yang or fire in the Heart and Liver. The Heart is thought to be the ruler of shen (神), which is equivalent to the mind or spirit. When there is too much yang or fire in the Heart, the shen will get affected, which distresses the mind and causes emotional disorders like insomnia. This is why TCM physicians usually prescribe medicines that reduce the fire and nourish the yin when treating insomnia. 

Ideal Bedtime Based on TCM’s Sleep Cycle  

While wei qi circulates the body, it goes through the meridians (the channels where our qi, blood and body fluids move). Wei qi does this 25 times along yang meridians during daytime and then 25 more times throughout yin meridians at night-time.

When wei qi flows through a meridian, it will spend around two hours in it. There, wei qi will vitalise and strengthen the organs correlated with the said meridian. Afterwards, wei qi will resume its journey to the next meridian, where it will repeat its action to nourish other organs.

The chart below depicts which meridians wei qi visits and the organs it interacts with during its 24-hour circulation. Using the meridian clock as a basis, we can determine the best time to sleep according to TCM, which is by 11pm.  

1am – 3am	Liver
3am – 5am	Lungs
5am – 7am	Large intestines
9am – 11am	Spleen
11am – 1pm	Heart
1pm – 3pm	Small intestines
3pm – 5pm	Bladder
5pm – 7pm	Kidneys
7pm – 9pm	Pericardium (Fibrous sac that encloses the heart and great vessels)
9pm – 11pm	Triple burner (The system that manages the movement of water)
11pm – 1am	Gall bladder

The chart above can also identify if there’s a disruption in the organ systems. If sleep constantly gets disturbed at a particular hour, it may indicate trouble in the corresponding organ. 

A good night’s rest is vital well-being, and to achieve that, you need to maintain a healthy sleep cycle. Your job or life demands may keep you awake for many hours, and you may not know when to take a break. But you shouldn’t forgo your rest, as sleep is necessary to revitalise and strengthen your organs according to TCM.

This is an adaptation of an article, “Natural Rhythm of Yin and Yang in Our Body”, which first appeared on the Eu Yan Sang website.