Why do we sleep, what happens during sleep?

No one knows the full benefits of why we sleep, but it is probably necessary for many biological reasons such as -

• Energy conservation

We need sleep to conserve energy. By sleeping we can reduce our calorie needs by spending part of our time working at a lower metabolism. This concept is based on how our metabolic rate drops during sleep. Research shows that for humans, 8 hours of sleep can result in daily energy savings of 35 percent over waking hours. The energy conservation theory of sleep states that the main purpose of sleep is to reduce a person's energy use during the day and night.

• To repair cells

Another theory, called the restorative theory, says that the body needs sleep to restore itself. Sleep allows cells to repair and regrow. This is supported by many important processes that occur during sleep, including:

• muscle repair

• protein synthesis

• tissue growth

• hormone release

• Helpful in better brain function

Brain plasticity theory states that sleep is essential for brain function. Specifically, sleep allows neurons, or nerve cells, to reorganize. While we sleep, the brain's glymphatic (waste clearance) system clears waste from the central nervous system. Sleep flushes out toxic products that accumulate in the brain throughout the day. Due to this, when we wake up, the brain is able to work well. Research shows that sleep helps restore memory by converting short-term memories into long-term memories, as well as by erasing or forgetting unnecessary information. Sleep affects many aspects of brain function, including:

• Learn

• Remember

• problem solving skills

• creativity

• decision making

• stay in the center

• concentration

• emotional well-being

Similarly, sleep is essential for emotional health. During sleep, brain activity increases in areas that regulate emotions, 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, helps in the fear response. It controls your response when you encounter a stressful situation. When we get enough sleep, the amygdala responds in a more adaptive manner. Research shows that sleep and mental health are linked.

• Aids in weight maintenance

Sleep helps in maintaining weight balance by controlling hunger hormones. These hormones include ghrelin, which increases appetite, and leptin, which increases the feeling of fullness after eating. During sleep, ghrelin decreases because you are using less energy than when you are awake.

Lack of sleep increases ghrelin and suppresses leptin. This imbalance leads to increased hunger, which can lead to eating more calories and increasing the risk of weight gain. Recent research suggests that lack of sleep may be associated with the following risks:

• obesity

• metabolic syndrome

• diabetes type 2

• Promote proper insulin function

Insulin is a hormone that helps cells use glucose or sugar for energy. But in insulin resistance, cells do not respond properly to insulin. This can lead to high blood sugar levels and, ultimately, increase the risk of developing type 2 diabetes. Sleep may protect against insulin resistance. It keeps your cells healthy so that they can easily absorb glucose. The brain also uses less glucose during sleep, helping the body regulate overall blood glucose.

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• Helpful in increasing immunity

A healthy and strong immune system depends on sleep. Research shows that lack of sleep can disrupt the immune response and make the body more susceptible to germs. When we sleep, our body makes cytokines, which are proteins that fight infection and inflammation. It also produces some antibodies and immune cells. Additionally, sleep prevents disease by destroying harmful germs. That's why sleep is so important when we're sick or stressed. At such times the body needs even more immune cells and proteins.

• Helpful for heart and brain health

Scientists believe that sleep is helpful in heart health. The Centers for Disease Control and Prevention (CDC) says the average adult needs 7 hours of sleep a night. Getting less sleep than this can lead to health problems, many of which can harm your heart health.

Lack of sleep is linked to risk factors for heart disease, including:

• high blood pressure

• increased activity of the sympathetic nervous system

• increased swelling

• elevated cortisol levels

• gaining weight

• insulin resistance

Read more - (Ayurvedic Tips for Good Sleep)

Our body goes through four stages of sleep. This cycle occurs several times throughout the night for varying periods of time, with each phase lasting from 70 to 120 minutes. These stages are typically repeated about four to five times during a 7 to 9 hour sleep period.

The pattern includes two major stages of sleep: non-rapid eye movement (non-REM) sleep and REM (rapid eye movement) sleep. The four stages of sleep include three stages of non-REM sleep and one stage of REM sleep.

As the name suggests, there is an absence of eye movements in non-REM sleep, whereas in REM sleep, when dreams occur, there are rapid eye movements.

The four stages of sleep are as follows:

• Stage 1: Non-REM sleep

Stage 1 is when we first fall asleep. As our body enters light sleep, brain waves, heart rate and eye movements slow down. This phase lasts for about 7 minutes.

• Stage 2: Non-REM sleep

This stage involves light sleep just before deep sleep. In which body temperature decreases, eye movement stops, and heart rate and muscles become relaxed. Brain waves speed up for a while and then slow down. We spend the most time in Stage 2 during the night's sleep.

• Stage 3: Non-REM sleep

Deep sleep begins in stages 3 and 4. The eyes and muscles do not move and brain waves become even slower. Deep sleep is relaxing. The body replenishes its energy and repairs cells, tissues and muscles. So that we all can feel refreshed the next day.

• Stage 4: REM sleep

This stage first occurs about 90 minutes after falling asleep. During REM sleep your eyes move rapidly from side to side. In REM sleep, brain waves and eye movements increase. Heart rate and breathing also become faster. Dreams often occur during REM sleep. The brain also processes information during this stage, making it important for learning and memory.

Read more - (Benefits of Getting Enough Sleep)

The recommended amount of sleep depends on age. This may vary from person to person, but the CDC suggests the following duration based on age:

• From birth to 3 months: 14 to 17 hours

• 4 to 12 months: 12 to 16 hours per 24 hours, including naps

• 1 to 2 years: 11 to 14 hours per 24 hours, including naps

• 3 to 5 years: 10 to 13 hours per 24 hours, including naps

• 6 to 12 years: 9 to 12 hours

• 13 to 18 years: 8 to 10 hours

• 18 to 60 years: 7 or more hours

• 61 to 64 years: 7 to 9 hours

• 65 years and above: 7 to 8 hours

Read more - (Side Effects of Less Sleeping)

Without enough sleep, our body has difficulty functioning properly. Lack of sleep is linked to chronic health problems affecting the heart, kidneys, blood, brain and mental health. Lack of sleep is also linked to an increased risk of injury for both adults and children. For example, a drowsy driver can cause serious car accidents and even death. In older adults, poor sleep increases the risk of falls and broken bones.

Specific consequences of lack of sleep may include:

• mood changes

• Worry

• Depression

• poor memory

• poor focus and concentration

• Tiredness

• weak immune system

• weight gain

• high blood pressure

• insulin resistance

• chronic diseases, such as diabetes and heart disease

• increased risk of early death

Read more - (Which Foods Help You Sleep Better)

Sleep keeps us healthy and functioning well. It helps repair, restore and re-energize your body and brain. If we do not get enough sleep, we may experience side effects such as poor memory and focus, weak immunity and mood swings.

Most adults need 7 to 9 hours of sleep each night. If you're having trouble sleeping, talk to your doctor or sleep specialist. They can determine the underlying cause and help improve the quality of your sleep.