Hahahaha! Why does your expression look so ugly when you're asleep?

Everyone must have had ugly photos of themselves sleeping taken by their family members (it doesn’t matter if you haven’t). In the photos, they look weird while sleeping and have no expression control. They are obviously sleeping peacefully, so why do they look so ugly when they are asleep?

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Facial expression management failure when sleeping

Because facial muscles also need rest

If you want to know why you have a bad sleeping posture, you must first understand what changes happen to our body after we fall asleep.

In fact, our sleep is not in units of a whole night, but in cycles of about 90 minutes, with 4 to 6 cycles of sleep in one night.

When you first fall asleep, your body enters a non-rapid eye movement (NREM) phase dominated by slow-wave sleep. Depending on the depth of sleep, the NREM phase can be divided into three different periods. (The new guidelines divide it into three phases)

Stage 1: The stage of falling asleep, which usually lasts 1-7 minutes. It is very easy to wake up in this stage, and the muscle tension begins to weaken, but you can still make simple movements. In class or during a meeting, if you suddenly start nodding and dozing off, it is because you have entered this stage.

Stage 2: In the initial sleep cycle, this stage can last about 10-25 minutes and will be longer as the cycle increases. This stage is slightly more difficult to wake up than stage 1, muscle tone becomes weaker, and occasional spasms may occur.

Stage 3: Stage 3 lasts about 20-40 minutes. Stage 3 is often referred to as the "deep sleep" stage. It is not only difficult to wake up at this time, but the muscles of the whole body are also in a very relaxed state. Therefore, it is really difficult for the brain and facial muscles to manage facial expressions during the deep sleep stage.

When a non-REM period ends, the body does not immediately start the next cycle, but instead enters a state of "micro-wakefulness" from a deep sleep state.

If you open the eyelids of a sleeper in this state, you can observe that his eyeballs are moving back and forth quickly, so this period is also called rapid eye movement (REM). Like the deep sleep stage, muscles continue to remain in a resting state during REM sleep, and only some small muscles, such as the middle ear muscles and facial muscles, retain some activity. However, it is precisely because of these "awake" muscles that we unconsciously show strange expressions in our sleep.

Is the painful expression due to a nightmare?

In deep sleep, because muscles are relaxed, most people will remain expressionless during the sleep, but there are exceptions.

A small sample study of 29 healthy adults found that muscles contract during rapid eye movement to make frowning movements. But interestingly, when the researchers woke up healthy people who frowned in their sleep and asked them to immediately recall and evaluate their dreams, they found that these people were not actually experiencing negative dreams. Frowning in dreams seems to be just a "small movement" of the muscles themselves.

E0: EMG activation but no observable facial movement; E1a: brief (<1 second) frown; E1b: prolonged (>1 second) frown; E2: eyebrow raised Image source: Reference 2

Not only adults like to frown in their dreams, but even innocent babies like to frown in their dreams. Researchers recorded the expressions of 12 healthy babies in their sleep and found that they frowned almost three times as often as they smiled!

Although unconsciously frowning in sleep has nothing to do with nightmares and does not reflect a person's recent mental state. It is a very normal muscle activity, but rapid eye movement sleep behavior disorder makes people wear a "mask of pain" in their dreams.

For patients with REM sleep behavior disorder, the muscles that should have rested during REM sleep start working in conjunction with their dreams, so when nightmares come, they will show painful, sad and angry expressions in their dreams, and perform some violent behaviors such as punching and kicking. Sometimes they will also talk loudly, cry or yell in their dreams. If you wake these patients up when they show painful expressions, they will often tell you that they were experiencing a very terrible dream just now.

Rapid eye movement (REM) sleep behavior disorder patients will show pain, crying in pain, sadness and anger in their sleep. Image source: Reference 2

Smiling while sleeping is not necessarily a good thing

Our expressionless faces and frowning brows make us look unsweet when sleeping, but do the beautiful sleeping faces of princesses or princes with smiles on their faces described in novels really exist?

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The reality is that it is very rare for normal people to smile sweetly in their sleep.

Researchers once recruited 100 healthy people, 22 sleepwalkers and 52 patients with rapid eye movement sleep disorder, and then looked for smiles by recording the movements of their eye muscles.

During the experiment, the researchers recorded a total of 173 happy expressions, of which 43 (24.8%) were gentle smiles, 51 (29.5%) were open-mouth smiles, and 79 (45.7%) were laughs. And the researchers found that only 8% of healthy people actually show happy expressions in their sleep.

People with REM sleep disorder show happy expressions much more frequently, and their smiles are more diverse, including unilateral crooked smiles, smiles, open-mouth smiles, and chuckles.

RBD patient's smile 0=neutral expression, 1=squinting smile, 2=smiling, 3=open mouth smile, 4=laughing out loud Image source: Reference 5

Therefore, don’t force yourself to smile sweetly in your sleep. The most important thing is to ensure high-quality sleep!

What is sleeping with eyes open?

Some people may ask, why do some people have their eyes slightly open even though they are asleep?

About 5% of people do sleep with their eyes open, a condition called nocturnal lagophthalmos, named after the myth that rabbits never close their eyes when they sleep.

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Doctors believe that there are many reasons for sleeping with eyes open, such as:

Exophthalmos: Because the eyeball bulges out due to thyroid disease or other reasons, the eyelid may not be able to fully cover the bulging eyeball.

Scarring blepharoplasty: Eyelid function may be limited due to ocular trauma, surgery, or chemical burns.

Paralytic blepharoplasty: Eyelid problems can occur due to Parkinson's disease, infection, Bell's palsy and other facial nerve problems, excessive drinking and sedatives.

So, if you are troubled by this problem, it is best to consult a doctor.

References

[1]InstituteofMedicine(US)CommitteeonSleepMedicineandResearch.SleepDisordersandSleepDeprivation:AnUnmetPublicHealthProblem.ColtenHR,AltevogtBM,editors.Washington(DC):NationalAcademiesPress(US);2006.PMID:20669438.

[2]MaranciJB,AusselA,VidailhetM,ArnulfI.Grumpyfaceduringadultsleep:Acluetonegativeemotiond uringsleep?JSleepRes.2021Dec;30(6):e13369.doi:10.1111/jsr.13369.Epub2021Apr29.PMID:33928717

[3]PerlisML,GilesDE,FlemingGM,DrummondSP,JamesSP.SustainedfacialmuscleactivityduringREMsleepanditscorre lationwithdepression.JAffectDisord.1995Dec18;35(4):163-71.doi:10.1016/0165-0327(95)00065-8.PMID:8749981.

[4] Challamel, M.-J.andS.Lalhou, Spontaneoussmilingandfacialmimicsintheneonate:Acontributiontothefunctionalroleofparadoxicalsleepduringdevelopment.NeurophysiologieClinique, 2018.48(3):p.131.

[5]CléM,MaranciJB,WeynBanninghS,LanfranchiJ,VidailhetM,ArnulfI.Smilingasleep:Astudyofhappyemotionalexpr sessionsduringadultsleep.JSleepRes.2019Aug;28(4):e12814.doi:10.1111/jsr.12814.Epub2019Jan6.PMID:30614101.

[6]https://www.allaboutvision.com/eye-care/eye-anatomy/your-eyes-while-sleeping/

[7]https://opt-knowledge.com/lagophthalmos/

This article is a work of Science Popularization China-Starry Sky Project

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

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

Author: Hardy, PhD in Neurobiology, Zhejiang University

Review | Peng Zhiping Director of the Science Department of the China Sleep Research Society

Tang Qin, Director and Researcher of the Science Popularization Department of the Chinese Medical Association