My friends, it’s so comfortable to turn on the air conditioner and sleep under a quilt!

After the beginning of autumn, the weather has become much cooler in the morning and evening. I thought I could sleep without the air conditioner at night to save some electricity bills, but I ended up turning on the air conditioner and wrapping myself in a blanket to sleep. I asked my friends around me and found that many of them made the same choice as me, and their reasons were exactly the same as mine - turning on the air conditioner and covering myself with a blanket makes me sleep better! Is this true?

Turn on the air conditioner and cover yourself with a blanket

Sleeping is indeed more comfortable

Comparing the two situations of "not turning on the air conditioner and not covering the quilt" and "turning on the air conditioner and not covering the quilt", we will find that:

Don’t turn on the air conditioner or cover yourself with a blanket - the ambient temperature is too hot, which not only makes you sweat easily, but also makes you very restless and you really can’t fall asleep. And if you don’t cover yourself with a blanket, you always feel like something is missing in your stomach, and you feel insecure and can’t fall asleep.

Turn on the air conditioner without covering yourself with a blanket - the ambient temperature is low, but your body will feel chilly and curl up into a ball, making it difficult to fall asleep.

Image source: https://unsplash.com/ Photographer: Gregory Pappas

Therefore, it is most comfortable to sleep with the air conditioner on and a quilt under your body!

In fact, this is not just your feeling. Studies have also found that sleeping with the air conditioner on and a quilt under you is indeed more comfortable!

During the 20 years from 1984 to 2004, Switzerland, the Netherlands and Japan conducted three experiments to study the relationship between sleep and temperature. The results showed that lower ambient temperature does make it easier for people to fall asleep .

When we are covered with a quilt, the optimal temperature of the outside environment is between 19℃ and 22℃, while the optimal temperature inside the quilt is between 31℃ and 35℃. This temperature difference of about 10℃ between the inside and outside of the quilt is the most comfortable sleeping temperature for the human body! [1]

Why does a temperature difference of 10°C make the human body feel most comfortable? Researchers say this is because the body, quilt and environment are constantly exchanging heat to achieve a dynamic thermal balance , so that the core part of our body always maintains a temperature range that is most suitable for sleep.

In early autumn, the indoor temperature of 19℃～22℃ can only be achieved by turning on the air conditioner. The bed temperature of 31℃～35℃ can only be achieved by covering the bed with a quilt. Therefore, it is indeed more comfortable to sleep with the air conditioner on and the quilt covered!

Cover with a thicker quilt

Falling asleep faster

A study conducted by Swedish researchers shows that sleeping with a quilt is indeed beneficial to sleep compared to sleeping without a quilt, and we fall asleep faster if we cover ourselves with a slightly thicker quilt.

The researchers asked 26 healthy subjects to cover themselves with two types of quilts. The first type was a thick quilt, which weighed about 12% of the subjects' body weight, and the second type was a thin quilt, which weighed about 2.4% of the subjects' body weight. Then they monitored the increase in melatonin concentration in the subjects' oral saliva within one hour before they fell asleep.

The results showed that the concentration of melatonin in the saliva of the subjects covered with thick quilts increased faster . Since melatonin is a sleep-inducing hormone secreted by the pineal gland in the brain, when the concentration of melatonin increases, people are more likely to fall asleep. This means that the subjects covered with slightly thicker quilts will fall asleep faster.

Why does a thick quilt help you fall asleep? Researchers believe that this may be related to the "pressure" that a thick quilt brings to the body . Because the quilt is thick and presses on the body, the sensory nerve cells on the skin feel pressure, and these sensory nerve cells transmit signals to the pineal gland in the brain, prompting an increase in the secretion of melatonin.

Other studies have shown that the pressure stimulation caused by covering the body with a thick quilt will increase the excitement of the parasympathetic nerves of the autonomic nervous system, while reducing the excitement of the sympathetic nerves, which has a calming effect and can help the body relax .

Other studies have shown that the pressure stimulation caused by covering the body with a thick quilt can increase the secretion of oxytocin in the body, thereby producing anti-anxiety and sedative effects .

Change to a thick quilt

Can effectively improve sleep quality

Falling asleep quickly, sleeping well, and sleeping through the night are very happy things. However, in modern society, more and more people are experiencing a "sleep crisis": insomnia, difficulty falling asleep, shallow sleep, waking up easily, being unable to fall asleep again after waking up, waking up too early in the morning... These sleep problems are bothering more and more people.

Not long ago, a journal called "Journal of Clinical Sleep Medicine" (JCSM) under the American Academy of Sleep Medicine made a suggestion for people with poor sleep quality: you might as well try changing to a thick quilt, and stick to it for a month, and your sleep quality may improve.

Image source: https://unsplash.com/ Photographer: taisiia shestopal

Still in Sweden, researchers at the Karolinska Institute recruited 120 subjects with clinical insomnia and at least one mental illness (such as anxiety, bipolar disorder, and major depression). The 120 subjects were randomly divided into two groups. The subjects in the experimental group were covered with thick quilts weighing 8 kg or 6 kg, and the subjects in the control group were covered with thin quilts weighing 1.5 kg. All subjects were asked to sleep with these quilts. The experiment lasted for 4 weeks.

After 4 weeks, nearly 60% of the subjects in the experimental group covered with thick quilts had their insomnia symptoms relieved by 42.2%, while in the control group covered with thin quilts, only 5.4% of the subjects had their insomnia symptoms relieved by 3.6%.

When some of the subjects were transferred from the control group to the experimental group and changed from covering with thin quilts to covering with thick quilts, their insomnia symptoms were significantly alleviated .

After the 4-week experiment, the research team continued to conduct a 12-month follow-up and found that most of the subjects in the experimental group continued to use thick quilts in their daily lives during these 12 months, and 92% of them had a positive change in their sleep conditions, and 78% of them had their insomnia symptoms effectively relieved.

So, if you are suffering from insomnia, you might as well try changing to a thicker quilt. Maybe your insomnia symptoms can be greatly relieved.

It is not good to have a quilt that is too thick or too thin

What is the optimal thickness?

So, how thick a quilt should be to help you sleep? Studies have found that a quilt that is too thick or too thin will not help you sleep.

If the quilt is too thick, the weight will compress the chest, affecting breathing and making people feel suffocated ; a quilt that is too thick will also affect the body's heat dissipation, causing the temperature inside the quilt to be too high. People will feel hotter and hotter as they sleep, sweat more, and have a bad sleep experience.

If the quilt is too thin, you may not feel anything when covering your body, and you may feel psychologically insecure when sleeping; and thin quilts have poor insulation effects. The body surface and soles of the feet are easily stimulated by the cold, and the cerebral cortex is always in an excited state, making it more difficult to fall asleep, or waking up frequently in the middle of the night, resulting in shallow sleep.

Since a quilt that is too thick or too thin is not good, what is the optimal thickness?

Image source: https://unsplash.com/ Photographer: elizabeth lies

In fact, there is no absolute numerical standard for the thickness of a quilt. It is related to the weight of the person who covers the quilt. Studies have found that when the weight of a quilt is 7% to 12% of the body weight (kg) , it is the most comfortable and most conducive to sleep . In other words, if a 60 kg adult, the weight of the quilt may be optimal when it is 4.2 to 7.2 kg.

But this weight is not so absolute. The weight of the quilt also needs to be adjusted according to the indoor ambient temperature, indoor air humidity, and the material of the quilt.

If you are in the central region of my country where the air humidity is high and the indoor temperature is low, the quilt can be thicker; in the northern region where there is heating, the indoor temperature is high and the air is dry, the quilt can be thinner; in the warm and humid southern region, the quilt thickness is moderate.

Different quilt materials have different suitable weights. For example, cotton quilts have better warmth retention and comfort, and you feel comfortable and warm when covered with them. However, they also have disadvantages. For example, if they are too thick, they will compress the chest. It is not recommended for people with cardiovascular and cerebrovascular diseases or those who are prone to breathing difficulties to cover themselves with too thick cotton quilts.

Down quilts are very light, and have good warmth retention, moisture absorption, and perspiration permeability. They are especially suitable for the humid south and people who sweat a lot when sleeping. It is more appropriate to choose a down quilt that is about half the weight of a cotton quilt.

Synthetic fiber quilts are very light, but they easily generate static electricity when rubbed. Therefore, when it is warm and dry in the north, it is not recommended to cover yourself with a synthetic fiber quilt to avoid causing dry and rough skin.

Silk quilts are soft, light, and comfortable. They also have certain anti-mite, antibacterial and anti-mildew effects. However, they have poor elasticity and are not thick. They are more suitable for use in summer and autumn. You may feel cold using them in winter.

Wool quilts are very close-fitting and suitable for people who sleep restlessly. They are highly hygroscopic and can also resist bacteria and mites, making them suitable for people who sweat a lot.

How to clean and maintain different types of quilts?

No matter what type of quilt you use, it is easy to get dusty, absorb moisture, grow bacteria and mites when you cover yourself with it. Therefore, the quilt cover and quilt surface need to be cleaned frequently, preferably once every half a month .

At the same time, it is not recommended to wash the quilt core too frequently, otherwise it will affect the fluffiness of the quilt core, making it uncomfortable to cover and reducing its warmth retention. Experts recommend that the frequency of cleaning different types of quilt cores is as follows: the quilt cores of synthetic quilts and cotton quilts can be washed once a year, the quilt cores of down quilts can be washed once every 2 to 3 years, and the quilt cores of wool quilts and silk quilts are best not to be washed.

In addition to cleaning the quilt cover, quilt cover, and quilt core, it is also recommended to frequently hang the quilt in a place with direct sunlight and ventilation to dry it in order to remove bacteria and mites and keep the quilt dry, soft, fluffy, and clean.

Cotton quilts have strong moisture absorption, so you can choose to expose them to the sun for 3 to 4 hours around noon when the sun is the strongest. Synthetic quilts have low humidity, so you can expose them to the sun for a shorter period of time, 2 to 3 hours is enough.

Wool blankets are also susceptible to moisture and insects, but they are not as resistant to sunlight, so they can be exposed to mild sunlight for about 2 hours between 9 and 11 a.m.;

If the down quilt and silk quilt are exposed to the sun, the fibers will be easily damaged, so it is best to choose the softer sunlight in the morning and evening, and air it for 1 to 2 hours. After the above quilts are dried, they should be patted to shake off the corpses of bacteria and mites and excrement, so as to restore the fluffy and soft core of the quilt.

Finally, I wish everyone a peaceful and healthy sleep!

References

[1]Harding, EC, Franks, NP, & Wisden, W. (2019). The Temperature Dependence of Sleep. Frontiers in neuroscience, 13, 336.

Planning and production

Author: Zeng Xinyue, popular science creator

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

Planning丨Cui Yinghao

Editor: Cui Yinghao