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As the number of chilly days increases, many of you may be thinking, "It's time to switch to winter bedding." This article will introduce how to choose winter bedding that enhances sleep quality, including variations in winter bedding materials and points to check.
Do I need a winter duvet?
First, let's consider the question, "Is it necessary to change bedding between summer and winter?"
Japan has four distinct seasons, a climate rare in the world
Looking at the architectural structures of foreign countries, buildings in tropical regions often have good ventilation and long eaves for shade, while buildings in cold regions often have highly airtight structures to prevent heat from escaping. Thus, houses around the world are built to suit either summer or winter climates.
However, Japan has four distinct seasons, with muggy summers comparable to Southeast Asia and winters exposed to cold comparable to Northern Europe. Therefore, measures for both summer and winter are necessary. Because of this, Japan is said to be a country with rare climatic conditions globally, requiring insulation measures for both summer and winter. Given such an environment, bedding also needs to be changed according to the season.
Cold has a significant impact on sleep
First, "sleep stages" are indicators of sleep state, dividing sleep into stages based on features such as brain waves, eye movements, and electromyograms. Generally, sleep is classified into a total of five stages: REM sleep (the body is resting, but the brain is awake) and non-REM sleep (both brain and body are in deep sleep), which is divided into four stages.
Studies have shown that when sleeping naked without bedding or pajamas, exposed to room temperature changes, the time spent awake during sleep increases as the room temperature drops below 29°C, which is the temperature at which the body can maintain its temperature solely through thermoregulation.
Furthermore, when room temperature is lowered by the same temperature range, the awake time increases by more than double when lowered from 21°C compared to a high temperature of 37°C. Additionally, it was found that when the skin is warmed or cooled, the effect on sleep is greater with cooling than with warming.
From these results, it can be inferred that cold (low temperature environment) has a greater impact on sleep than heat (high temperature environment). Therefore, it is necessary to pay attention to bedding in autumn and winter to create a comfortable sleeping environment.
When do I need a winter duvet and until when?
When starting to use winter bedding, pay attention to the room temperature, not the outside temperature. Most people probably use heating or cooling indoors, so room temperature is the key point.
When do I need it?
There is no clear rule, but it is said that using a winter duvet when the room temperature drops below 15 degrees Celsius can provide comfortable sleep.
Until when do I need it?
Again, there is no clear rule, but it seems okay to put away your winter duvet when the temperature rises above 15 degrees. Many people seem to use it until around March.
Types of Winter Duvets (Down Duvets) Explained
When you think of winter duvets, the first thing that comes to mind is probably a down duvet. Light and warm down duvets are essential items for good quality sleep. However, there are various types of down. Each type has its own advantages and disadvantages, so find the material that suits you best.
Ratio of Down to Feathers
Generally, the filling of a down duvet consists of "down" blended with "feathers," and the ratio of down to feathers varies depending on the duvet. A duvet with 50% or more down and 50% or less feathers is called a "down duvet," and a duvet with less than 50% down and 50% or more feathers is called a "feather duvet."
Some manufacturers display "down duvets" and "feather duvets" interchangeably, and some down duvets are sold with silk floss blended instead of feathers.
Difference between Down and Feathers
"Down" refers to the soft, fluffy feathers found on the breast of waterfowl, and is characterized by its excellent warmth and insulation properties. A higher down ratio increases fluffiness and warmth, but also tends to increase the price.
"Feathers" are the quills from the wings of waterfowl, and generally have the stiff central shaft we commonly associate with feathers. They offer excellent moisture absorption and release, but have low insulation properties. Their elasticity helps reduce costs when blended and also prevents the duvet from losing its shape.
If you're looking for warmth, choose a duvet with a high down ratio. Also, the warmth and price of both down and feathers vary depending on the type of waterfowl used.
Duck (Duck Down)
Relatively affordable, but the down clusters are small, so a bulky duvet will be heavy. Also, since it uses feathers from omnivorous ducks, there may be an odor concern.
Goose (Goose Down)
Compared to duck down, it offers superior warmth and lightness. Additionally, as it's from herbivorous geese, there's less odor concern, but many products are more expensive than duck down.
Mother Goose (Feathers from adult geese)
Characterized by being very light despite its voluminousness. It releases heat on warm days and stores it on cold days, maintaining a comfortable temperature. However, it is expensive due to being rare down carefully harvested by hand.
Eiderdown (Down collected from the nests of wild birds living in the Arctic Circle)
Eiderdown, often called the finest quality down duvet, is extremely rare because it is collected from the nests of wild birds living in the frigid Arctic Circle. It is an ultra-luxury item, with some products costing millions of yen.
Does a winter duvet change the quality of sleep?
Earlier, we mentioned that awakening time during sleep tends to be longer in cold environments. But does the use of winter duvets and sleepwear change the quality of sleep?
If bedding provides sufficient insulation, low temperatures do not affect sleep stages.
If the bedding has sufficient insulation, even with a 10°C difference in room temperature, the difference in bed temperature will be minimal, so low temperatures will not affect sleep stages. Furthermore, research has shown that with proper use of bedding, no impact is observed up to 3°C for young people.
In other words, it is more important to maintain a comfortable bed temperature than room temperature, and specifically, it is crucial to use bedding and sleepwear appropriate for the season.
In cold environments, the cold and damp sensation upon entering bed can hinder sleep, so touch and feel are also important.
In cold environments, the characteristics of bedding are said to affect thermoregulation, and in particular, the cold and damp sensation upon entering bed is thought to potentially hinder sleep onset. It is also said that using bedding with a pleasant texture enhances subjective sleep quality.
Be careful not to overheat!
As a way to deal with cold environments, using bed heating devices like electric blankets is recommended. However, an overheated bed temperature can be a burden on the body, so use it to warm the futon before going to bed and turn off the power when you fall asleep.
In cold environments, it is believed that if the bedding provides sufficient insulation, it will not affect sleep stages. However, it is recommended to maintain the room temperature at least above 10℃. Especially for older people, it is important to eliminate the temperature difference between the bedroom and the toilet, considering night-time trips to the bathroom.
How to improve sleep quality with bedding?
To improve sleep quality in cold environments, it's essential to choose a duvet that can keep you warm when you go to bed, and then effectively release heat and moisture to prevent stuffiness once you're asleep. In addition to warmth and moisture-wicking properties, also consider lightness to avoid burdening your body, and ease of washing to maintain cleanliness.
Summary of How to Choose Winter Duvets
In Japan, with its four seasons, using bedding appropriate for each season can lead to good quality sleep. Especially in the cold winter environment, it is crucial to use a winter duvet. However, not just any winter duvet will do. In addition to being light and warm, also check for breathability to prevent stuffiness and ease of washing to maintain cleanliness.
Prepare your winter bedding and enjoy comfortable sleep.
