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When the cold winter season arrives, many people may feel like they "can't fall asleep easily" or "their sleep quality has declined." And there's a good reason for that: winter is actually a season when sleep quality tends to decrease.
In this article, we'll introduce the mechanisms you should know about and recommended items to improve your sleep quality in winter.
Mechanism of Decreased Sleep Quality in Winter
First, let's look at the causes and mechanisms of decreased sleep quality in winter.
1: The Key is "Core Body Temperature"
When awake, the difference between skin temperature (perceived temperature of the face and extremities) and core body temperature (internal body temperature) is about 2℃. However, at the onset of sleep, the core body temperature drops, narrowing the difference to about 1.2℃. This change in core body temperature switches off the wakefulness mode and switches to sleep mode.
2: How People Get Sleepy (Relationship Between Sleep and Core Body Temperature)
As mentioned earlier, the difference between core body temperature and skin temperature fluctuates between day and night. During the day, core body temperature is high and skin temperature is relatively low. However, when falling asleep, skin temperature rises and core body temperature drops. This is because the body needs to radiate heat from within to the outside by increasing blood flow within the skin.
The smaller the difference between core body temperature and skin temperature, the stronger the sleepiness and the higher the quality of sleep.
3: Why People with Cold Sensitivity Have Trouble Falling Asleep
Normally, the body lowers core body temperature by releasing internal heat through the capillaries in the skin. However, people with cold sensitivity have poor blood circulation in their hands and feet, which hinders this mechanism. As a result, the difference between core body temperature and skin temperature doesn't narrow easily, making it difficult to fall asleep.
Causes of cold sensitivity include dysregulation of the autonomic nervous system or hormonal balance, low blood pressure, and anemia. It's important to improve this by increasing muscle mass through exercise and making lifestyle changes such as diet and bathing. An immediate solution is to choose bedding that maintains a comfortable temperature inside the bed.
4: The "Sympathetic Nervous System" Becomes Dominant
The autonomic nervous system is also related to coldness and sleep quality.
Normally, as core body temperature drops towards bedtime, the body switches from the "sympathetic nervous system," which is active, to the "parasympathetic nervous system," which promotes relaxation and sleep. However, when the body is cold, the "sympathetic nervous system" remains dominant to prevent heat loss, which makes it difficult to fall asleep and can reduce sleep quality even during sleep, as the body cannot relax.
3 Reasons Why You Don't Warm Up Easily Even After Getting Into Bed
Many people find it difficult to warm up their hands and feet even after getting into bed. Here are the reasons why.
1: Heat Moves from Higher to Lower Temperatures
Heat naturally moves from areas of higher temperature to areas of lower temperature. Therefore, the heat inside the futon, warmed by your body temperature, tries to move to the colder outside of the futon. The thermal conductivity (the rate at which heat moves) varies depending on the material of the futon. If you use a futon made of a highly thermally conductive material, heat will continuously escape, and the inside of the futon will never get warm.
2: Gaps Between the Duvet and Your Body
If there's a gap between your duvet and your body, warm air escapes from it, and cold air enters in turn.
Aside from the material of the duvet, if the outer fabric is stiff, or if it's new and crisp, it won't conform to your body. If cold air enters your duvet when you turn over, you might be able to sleep comfortably by switching to a duvet that prioritizes conformity.
Even down duvets, which are said to be warm, can have stiff outer fabrics due to down-proofing. So, choose one that prioritizes conformity. Also, blankets conform flexibly to your body, so using a blanket can eliminate that chilly feeling.
3: Getting Chilled from Sweating and Becoming Damp While Sleeping
If you layer many blankets and comforters to keep warm, they not only become heavy and burdensome for your body but also trap moisture.
Sweating during sleep itself is a physiological phenomenon that deepens sleep, so it's not a problem. However, it is said that "people sweat a cup's worth during sleep," and this sweat accumulates in the bedding. Not only does it make you damp, but the sweat can also cool your body and cause you to catch a cold while sleeping, so choose bedding that is warm and breathable.
Even if you use a good comforter, be careful if you use a duvet cover with poor water absorption and moisture permeability, as it can cause stuffiness. Choose bedding that balances warmth and humidity well.
This Winter, Power Shortages Require Energy Conservation & Potential for Soaring Electricity Prices
Winter, with its shorter daylight hours and lower temperatures, is the season when electricity consumption is highest throughout the year. While air conditioning is used in summer, the difference between outdoor and indoor temperatures is greater in winter, leading to higher electricity consumption. Let's also consider electricity and electricity prices this winter.
Power Shortages May Require Energy Conservation
According to announcements from the Ministry of Economy, Trade and Industry and the Agency for Natural Resources and Energy, concerns about power supply-demand tightness are expected for the winter of 2022-2023.
Although the reserve rate of electricity has recovered since the Shintaku Thermal Power Plant Unit 1, which was damaged in the March Fukushima offshore earthquake, is expected to be restored by the end of the year, areas other than Hokkaido and Okinawa still haven't secured the 3% reserve rate necessary for stable electricity supply. Therefore, it seems that everyone needs to be mindful of energy conservation this winter.
Electricity Prices Are Expected to Rise Even Further
Many people have already experienced the surge in electricity prices, and major power companies have announced that they are preparing to apply for government approval for further price increases towards 2023.
The electricity bill paid monthly includes a fuel cost adjustment charge (a fee that adjusts for fluctuations in the import prices of fuel used in thermal power plants). Since early 2021, the trade prices of crude oil, LNG (liquefied natural gas), coal, and other fuels imported from overseas have been rising, leading to soaring electricity prices.
Furthermore, as fuel costs for power generation also rise in proportion to electricity consumption, winter, which has the highest electricity consumption of the year, is also the season with the highest electricity bills.
【References】
※ "Stanford's Sleeping Classroom" by Seiji Nishino (Gentosha)
※ "Measures for Power Supply and Demand in FY2022" by Ministry of Economy, Trade and Industry
