Why do people fall asleep as soon as they get on the bus? It turns out that this is how they are "hypnotized"!

Have you ever had this experience: when you are on a bus, you can still look at the scenery outside the bus when you first get on, but after a while, you start to doze off.

Why do people feel sleepy so easily when riding in a car?

This starts with why people feel sleepy.

The alternation between a person's wakefulness and sleepiness is determined on the one hand by the body's biological clock and on the other hand by sleep pressure. Your brain is accumulating a substance called adenosine[4]. Adenosine is a product of cells using energy. Every second you are awake, your brain is consuming energy and adenosine is accumulating. The accumulated adenosine has an effect that makes you feel sleepy and want to sleep. This is what we call sleep pressure.

As the day progresses, adenosine levels build up, and once they reach a certain point, they inhibit the areas of the brain that promote wakefulness and activate the areas of the brain that promote sleep. For most people, that's usually 12-16 hours after waking up. After you fall asleep, your brain clears the adenosine from you, so you can wake up refreshed the next morning.

This is what we mean when we say that sleepiness is a function of both circadian rhythm and sleep pressure.

Diagram of sleepiness Source: Author

The blue line represents the circadian rhythm, which rises and falls regularly like a sine wave. The higher the blue line is, the higher the level of wakefulness the circadian rhythm brings you. After you wake up in the morning, the circadian rhythm will bring you to a more awake state.

For most people, the circadian rhythm wakefulness signal peaks before the afternoon. The orange line represents sleep pressure. The higher the orange line is, the greater the sleep pressure is. In the figure, the difference between the orange line and the blue line represents your sleepiness. The greater the difference, the stronger the sleepiness.

If on this basis, people also add the pressure of work, the pressure of life, the hard work of running around, etc., they will find ways to "catch up on sleep" whenever they have time.

Sitting in a car for a long time provides a signal to the brain: the environment is safe and relaxing, which can relieve sleep pressure.

Although the noise of the vehicle running can be heard inside the bus, this low-frequency vibration is close to the frequency of the brain's electrical activity when you are drowsy, which can gradually induce the brain to discharge at the frequency of "falling asleep" [1-3]. In addition, the space inside the bus is closed, the air circulation is poor, and the carbon dioxide concentration is high. When the brain is deprived of oxygen, it will feel more sleepy.

So can this short rest in the car help a tired body recover?

When people lack sleep, a short rest during the day can temporarily relieve sleep pressure. As the old saying goes, a nap is better than no nap. However, fragmented naps do not mean supplementing sleep.

Napping is a signal that reminds us that we should pay attention to our sleep conditions.

How can we improve our sleep in our busy lives?

1. Develop good sleeping habits

First of all, you should keep the bedroom environment comfortable, the temperature appropriate, and the ventilation good, form regular bedtimes and waking up times, maintain regular exercise, soak your feet in hot water before going to bed, avoid drinking stimulating beverages such as coffee and strong tea, and you can drink hot milk to promote sleep.

It is best not to drink water 2-3 hours before going to bed to avoid getting up at night. Drinking water too late can easily cause edema.

2. Practice sleep restriction

Appropriate sleep restriction can increase the patient's desire for sleep and improve sleep efficiency by shortening the time in bed.

Ensure adequate sleep time. To ensure a good sleep, adequate sleep time is essential. A normal adult sleeps 6-8 hours a day. You can take a 15-30 minute nap at noon. It is best to go to bed around 9 to 11 o'clock in the evening. 11 o'clock in the evening to 1 o'clock in the morning is the detoxification time of the kidneys, so it is best to stay in a deep sleep state.

3. Stimulus Control

It means going to bed only when you feel sleepy, and not doing any activities unrelated to sleep in bed or in the bedroom, such as watching TV, playing with mobile phone, etc. If you still cannot fall asleep within 20 minutes of going to bed, go to another room immediately, and return to bed when you feel sleepy. No matter how long you sleep at night, you must get up on time the next day and avoid taking naps during the day.

4. Relaxation therapy

It refers to the use of breathing or stretching relaxation activities to reduce tension and excessive alertness during sleep, so as to reduce the number of awakenings at night and improve the quality of sleep.

Avoid strenuous exercise before going to bed. 2-3 hours before going to bed, you can do some appropriate exercise, such as a short walk or simple yoga, which is good for falling asleep. However, strenuous exercise can easily make the brain excited, and strenuous exercise will make the whole body sweat and heat up, making it difficult to calm down quickly.

5. Music therapy

You can listen to soothing music[5] to reduce the excitability of the sympathetic nerves, relieve anxiety, tension and stress reactions, and promote sleep.

6. Create a comfortable sleeping environment

Turn off the lights when you go to bed. If you turn on the lights when you go to bed, the light will irritate your eyes and disturb your sleep. Therefore, it is best to turn off the lights when you go to bed.

Reduce noise. If we sleep in a noisy environment, we tend to toss and turn at night and it is difficult to ensure the quality of sleep. Therefore, it is best to sleep in a quiet place and wear earplugs if necessary.

When we have done these preparations before going to bed, we should also avoid having random thoughts. Before going to bed, we should empty our minds so that it is easier to fall asleep. If we think about some complicated problems before going to bed, we will become more and more excited.

Although we sometimes use playing with mobile phones to treat insomnia, it may be counterproductive. It is better to place the phone a little further away from the head to reduce interference with sleep, maintain physical strength, and prepare for a new life the next day.

References:

[1]National Institute of Neurological Disorders and Stroke. Brain basics: Understanding sleep. Retrieved April, 2021, from https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Understanding-Sleep

[2]Bjorness, TE, & Greene, RW (2009). Adenosine and sleep. Current Neuropharmacology, 7(3), 238-245.

[3]Ribeiro, JA, & Sebastiao, AM (2010). Caffeine and adenosine. Journal of Alzheimer's Disease, 20(s1), S3-S15.

[4] Effects of Cuscuta australis extract on serum cytokines, SOD and MDA in insomnia rats[J]. Liu Haiyun; Fang Yongqing; He Zhijian; Wu Qinghua; Song Miaomiao; Lin Qianxia; Hou Benchao. Jiangxi Journal of Traditional Chinese Medicine, 2021(12)

[5] The relationship between the five personality traits and sleep quality of graduate students[D]. Huang Xiao. Wannan Medical College, 2022

This article is a work supported by Science Popularization China Starry Sky Project

Author: Xu Lang

Reviewer: Wang Qian, researcher at the Third Medical Center of PLA General Hospital

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.