Why Do We Sleep?
Sleep is as important to our survival as food and water, so it should come as no surprise that we spend about a third of our lives sleeping.
So what happens to our body when we sleep?
- The brain stores new information and gets rid of toxic waste.
- Nerve cells communicate and reorganize, which supports healthy brain function.
- The body repairs cells, replenishes lost energy, and releases molecules such as hormones and proteins.
These biological processes are so critical to our health that without them, our bodies would not be able to function properly.
In this article, we delve deeper into the importance of sleep in our physical and mental health, answer the question "why do we sleep" and analyze the complications that accumulated sleep deprivation can bring to our health.
Let's start!
Why do we sleep?
Even today, there is still much that remains unknown about the purpose of sleep. However, one thing that all scientists agree on is that the explanation for why we sleep does not have just one answer. There are many biological reasons behind the need for humans - and all living things - to sleep.
Currently, scientists have found that sleep helps the body in a variety of ways. The most prominent theories on the question of "why we sleep" are described below.
1. Conservation of energy
According to the conservation of energy theory, we need sleep to conserve energy. Sleep allows us to reduce our body's caloric needs by spending some of our time operating at a lower metabolic rate.
This idea is supported by the way our metabolic rate drops during sleep. Research suggests that 8 hours of sleep for human beings can produce a daily energy saving of 35% over fully awake .
The energy conservation theory of sleep suggests that the main purpose of sleep is to reduce the individual's energy expenditure during periods of time when they are not able to hunt for food, such as at night.
2. Cell restoration
Another theory, called the "restoration theory," says that the body needs sleep to restore itself.
The idea is that sleep allows cells to repair and regenerate. This is supported by several important processes that occur during sleep, including:
- Muscle recovery
- Protein synthesis
- The development of muscle tissue
- The release of hormones
3. Proper brain function
The theory of brain plasticity says that sleep is essential for brain function. Specifically, it allows neurons, or nerve cells, to reorganize.
When you sleep, our brain's lymphatic system (waste clearance) removes waste from the central nervous system and removes toxic byproducts from our brain that have accumulated during the day. This allows our brain to function well when we wake up and feel refreshed.
More specifically, research shows that sleep contributes to memory function by converting short-term memories into long-term memories, while deleting or forgetting unnecessary information that could otherwise confuse the nervous system.
Sleep affects many aspects of brain function, including:
- Learning
- Memory
- Problem-solving ability
- Creativity
- Decision-making ability
- Concentration
4. Emotional well-being
Similarly, sleep is essential for emotional health. During sleep, brain activity increases in areas that regulate emotions, thus supporting healthy brain function and emotional stability.
An example of how sleep can help regulate emotions occurs in the amygdala. This part of the brain, located in the temporal lobe, is responsible for the fear response and is what controls your reaction when faced with a perceived threat, such as a stressful situation.
So when you get enough sleep, the amygdala can respond in a more adaptive and milder way, whereas if you are sleep deprived, in a stressful situation it is very likely that the amygdala will overreact.
Research shows that sleep and mental health are interconnected. On the one hand, sleep disorders can contribute to the onset and progression of mental health problems, but on the other hand, mental health problems can also contribute to sleep disorders. The relationship is bidirectional.
5. Weight maintenance
Sleep also affects your weight by controlling hunger hormones. These hormones include ghrelin, which increases your appetite for food, and leptin, which increases feelings of fullness after eating.
During sleep, ghrelin decreases because you consume less energy than when you are awake. Lack of sleep, however, raises ghrelin and suppresses leptin, and this imbalance makes you hungrier, which can increase your risk of consuming more calories and ultimately gaining weight.
Recent research suggests that chronic sleep deprivation, even when it's as short as five nights of poor sleep, may be associated with an increased risk of obesity, metabolic syndrome, and type 2 diabetes.
6. Proper insulin function
Insulin is a hormone that helps cells use glucose as a source of energy for our bodies. By extension, lack of sleep causes disruptions in the insulin that regulates and metabolizes glucose, leading to high blood glucose levels and ultimately type 2 diabetes.
Good sleep can protect against insulin resistance and keep cells healthy so they can easily take up glucose. Additionally, the brain uses less glucose during sleep, helping the body regulate overall blood glucose.
7. Immunity
A healthy and strong immune system is heavily dependent on sleep. Research shows that sleep deprivation can inhibit the immune response and make the body susceptible to germs.
When we sleep, our bodies produce cytokines, hormones that fight infection and inflammation, as well as certain antibodies and immune system cells. All of these together prevent any potential illness by destroying harmful microbes.
That's why sleep is so important when we're sick or stressed. During these times, the body needs even more immune cells and proteins.
[Read: 8 Ways a Weighted Blanket Reduces Stress ]
8. Heart health
Although the exact reasons are not clear, scientists believe that sleep supports heart health. This is borne out by the link between heart disease and poor sleep.
The Centers for Disease Control and Prevention (CDC) reports that the average adult needs 7 hours of sleep per night. Getting fewer hours than that on a regular basis can lead to health problems, many of which can harm heart health.
Specifically, lack of sleep is associated with risk factors for heart disease, such as:
- High blood pressure
- Increased activity of the sympathetic nervous system
- Increased inflammation
- Increased cortisol levels
- Weight gain
- Insulin resistance
[Read: What is Sleep Debt and How to Get Rid of It ]
What happens when we sleep?
When we sleep, the body goes through four stages of sleep that repeat throughout the night. This cycle lasts from 70 to 120 minutes .
The pattern includes two main phases of sleep:
- Non-rapid eye movement (non-REM) sleep and
- REM (rapid eye movement) sleep.
As the names suggest, non-REM sleep is characterized by the absence of eye movements, while REM sleep, (which is also the stage in which we dream) is characterized by rapid eye movement and intense brain activity.
The four stages of sleep are summarized as follows:
Stage 1: Non-REM sleep
Stage 1 occurs when we first fall asleep. As your body enters light sleep, your brain waves, heart rate, and eye movements slow down.
This phase lasts approximately 7 minutes.
Stage 2: Non-REM sleep
This stage includes light sleep just before deep sleep.
Body temperature drops, eye movements stop, and heart rate and muscles continue to relax. In addition, brain waves increase briefly and then slow down.
During a night, we spend most of our sleep time in stage 2.
Stage 3: Non-REM sleep
Deep sleep begins in stages 3 and 4. The eyes and muscles do not move and brain waves slow down even further.
Deep sleep is restorative. Our body replenishes its energy and repairs cells, tissues, and muscles. This phase is essential for us to wake up in the morning feeling fresh and renewed.
Stage 4: REM sleep
This stage initially occurs about 90 minutes after we fall asleep. Our eyes move rapidly, our brain waves and heart rate increase, and our breathing also quickens.
The dreams we see in our sleep often occur during REM sleep. Our brain also processes information during this stage, making it important for learning and memory.
[Read: How to Increase Deep Sleep ]
How many hours of sleep do we need?
The recommended amount of sleep depends on age. It also varies from person to person, but reliable sources suggest the following hours of sleep based on age:
- 0 to 3 months: 14 to 17 hours
- 4 to 12 months: 12 to 16 hours
- 1 to 2 years: 11 to 14 hours
- 3 to 5 years: 10 to 13 hours
- 6 to 12 years: 9 to 12 hours
- 13 to 18 years old: 8 to 10 hours
- 18 to 60 years old: 7 or more hours
- 61 to 64 years old: 7 to 9 hours
- 65 years and older: 7 to 8 hours
What happens when we don't get enough sleep?
Without enough sleep each night, our bodies struggle to function properly. Lack of sleep is linked to chronic health problems that affect the heart, kidneys, blood, brain, and mental health .
Lack of sleep is also associated with an increased risk of injury for both adults and children. Driver drowsiness, for example, can contribute to serious traffic accidents and even death.
In adults, accumulated sleep deprivation has been associated with a wide range of health problems, including:
- cardiovascular problems
- the weakened immune system
- the highest risk for obesity and type II diabetes
- reduced ability to concentrate and poor memory
- mental health problems , such as depression and anxiety disorders
These diverse effects caused by sleep deprivation are strong evidence that sleep does not only have a biological purpose but is in fact, through its complexity, an essential component for the proper functioning of almost all of our body's systems.
Conclusion
Sleep keeps us healthy and allows our body and brain to repair, restore, and renew lost energy.
By sleeping the recommended hours every night, we have the ability to:
- to rest our body
- to recover from an illness
- to cope with stress
- to be able to solve problems that arise in our lives
- to enrich our memories and
- to improve our motor skills.
However, a good night's sleep is not only defined by how many hours we slept, but also by the quality of sleep.
Sleep is an opportunity to grow as a person, resolve issues that are not related to sleep, and grow spiritually.
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How do they work?
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As a result, the mind stops "racing", the heart rate drops, the mood improves and the body enters a state of complete relaxation.
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