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On the web page, I search for the "get a good night's sleep" emoji, and it shows people's sweet and happy smiles when they are asleep, which seems very reasonable.

…… Wait! So do we really smile when we fall asleep? Is the expression in sleep consistent with that in our daily life?

This "feeling" is actually wrong. A recent study of adults found that most people are more likely to frown and look grumpy when they sleep.

You probably look like this when you sleep. | Ref. 1 it is often difficult for us to know what our expression is when we fall asleep. In this experiment, the facial expressions of the subjects were recorded on video while they were asleep. Two electrodes are also placed on the muscles used for frowning to measure the electromyography of the frowning muscles during sleep. To put it simply, it is to watch people sleep, and to describe and score the expressions that appear during sleep.

The researchers collected sleep videos and physiological characteristics of 91 adult subjects for 114 nights. These included healthy subjects who had no problem sleeping, patients with obstructive apnea syndrome who snored loudly, patients with restless leg syndrome who twitched their legs while lying down, patients with rapid eye movement disorder (RBD), insomnia, idiopathic narcolepsy, Parkinson's disease, and so on.

RBD is a sleep disorder, which is manifested in dreaming (usually rapid eye movement (REM)). The body always shows some exaggerated movements, such as shouting, crying, dancing, punching and kicking, etc., and may even hurt yourself or your partner. This disease is easy to occur in people over the age of 60 and may be related to other neurodegenerative diseases such as Parkinson's disease.

Patients with RBD may have some violent movements in their sleep. | JAMANetwork / youtube all in all, the study divided subjects into four groups: no sleep disorder, sleep disorder, arousal disorder (DoA) that is easy to sleepwalk and wake up, and RBD mentioned above.

However, it turned out that all the subjects showed some frown. Even if you get a good night's sleep, you still frown frequently during REM.

The dark boxes in figures b and c show the number of frowns in REM. | Ref. 1, however, earlier, some people have studied whether they will smile when they sleep. In fact, they will smile occasionally. In their sleep, there is not only a smile with the corners of the mouth raised, but also a laugh with an open mouth, and some are even accompanied by laughter. People who dream REM also have more smiles. After waking up, people who smile in dreams report eating cake in their dreams, while people who don't smile in dreams dream about fights and quarrels. As a result, the researchers speculate that a smile while asleep may really have something to do with happy dreams (but not for sure).

Happy smiles may also appear at all stages of sleep. | Ref. 2 but judging from the frequency of smiling (0.023 / hour) and frowning (2.33 / hour), we may still be frowning more time when we fall asleep. You may be having a sweet dream, but the real expression when you sleep is still frowning.

However, for people with RBD sleep disorders, they may look "more painful" when they sleep. Studies have found that patients with RBD move their eyebrows more flexibly and frown more frequently for long periods of time in REM. And they not only frown, but also make other more negative expressions, which seem to be much more painful than healthy controls.

They changed their "pain masks" in seconds: frowning, pulling down the corners of their mouths, their eyes closed tightly, as if they were shouting, crying and moaning, and some even talked in their sleep and slapped themselves. It could be poor sleep, bad mood, or physical pain.

People with RBD show painful expressions that seem to be really painful. | Ref. 1, but for healthy people without sleep disorders, even a slight frown during sleep does not mean that they are in a bad mood or full of trouble. after all, studies have long found that fetuses and newborns are also prone to frowning during sleep. And even with a very occasional smile, it seems normal to have a grumpy face that looks awkward when you sleep.

You'd better put on the expression of "don't wake me up with the alarm clock". | | Giphy (but if you have a sleep disorder that bothers you, please choose to see a doctor in time) |

So do you know the look on your face when you sleep? If you know, please leave a message in the comments section and tell us how you know [dog's head squinting]

Reference:

[1] Maranci, Jean-Baptiste, et al. "Grumpy face during adult sleep: A clue to negative emotion during sleep?." Journal of Sleep Research 30.6 (2021): e13369.

[2] Cl é, Marion, et al. "Smiling asleep: A study of happy emotional expressions during adult sleep." Journal of Sleep Research 28.4 (2019): e12814.

[3] Emde, Robert N., and Kenneth L. Koenig. "Neonatal smiling, frowning, and rapid eye movement states: II. Sleep-cycle study." Journal of the American Academy of Child Psychiatry 8.4 (1969): 637656.

This article is from the official Wechat account: bring Science Home (ID:steamforkids), author: everything.

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