The Science of Sleep and Why Your Body Needs It: Part One

Just like our bodies need oxygen, food, and water, sleep is necessary for our health, well being, and frankly, our survival. But despite all of the science around the importance of sleep, many adults still don’t get the required amount. In fact, one in three adults in America don’t get enough sleep

This can be blamed on a number of things. From always being on the go, to excessive cell phone and electronic use, humans today live in a world that’s much different than that of our ancestors.

And just like our ancestors, sleep is simply something our bodies cannot go without. It’s the part of our lives that our bodies rely on to reset and restore important systems within the body. We need sleep to maintain the balance within our bodies.² This is also referred to as homeostasis.

Without this reset and restoration, things in the body start to go wrong quickly. And when we don’t get enough sleep on a regular basis, we put ourselves at an increased risk of developing several dangerous health conditions, many of which can have lasting effects on the mind and body.

If you find that you don’t get enough sleep on a regular basis, there are several proven ways that you can improve your sleep. And by doing this, you can improve your overall health. But first, there needs to be an understanding of why sleep is important, how much sleep is needed, and the risks of sleep deprivation. 

Why Do We Need to Sleep? 

While sleep feels restful to us, our bodies use this time to focus on certain processes that can only occur during sleep. These processes need to happen to allow us to function while we’re awake.

Simply put, we need sleep to survive. 

Sleep provides balance and functioning of the nervous system, immune system, and metabolism.² Furthermore, it’s been found to be responsible for three necessary functions:³ 

  • Detoxification of the brain and body

  • Replacement of energy in the body

  • Formation of memories

There are trillions of cells in the human body that function to allow us to live. Our cells are constantly growing and developing, and in doing so they produce waste products called free radicals. In small amounts, our bodies are equipped to manage and get rid of them. However, high amounts of free radicals, which can come from breathing in smoke and other toxins and pollutants, can increase the risk of cancer and other diseases.⁴

The primary time that our body flushes out free radicals and other toxins, especially within the brain, is while we sleep. 

Our bodies also use sleeping as a time to replenish energy sources. When we’re awake, our body primarily uses energy from the food we eat. But if we don’t eat enough that day or require more energy than we consumed, our body then turns to energy sources stored in the body. 

Energy in the form of sugar that’s stored in the body is called glycogen. While some of the energy stores are replaced while we’re awake, the prime time for replacement of glycogen in the liver and muscles is while we sleep.

The storage and creation of memories is the last primary function of sleep. While we sleep, our bodies take recent experiences and convert them into long-term memories. However, this process doesn’t occur throughout the entire time we sleep. It primarily occurs in the last stage of the sleep cycle, which is REM sleep.⁵

What Are the Stages of Sleep?

The sleep cycle is made up of four different stages of sleep. These stages fall into two categories: rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep, which consists of three stages.

After falling asleep, people first cycle through the three stages of NREM sleep. This usually takes about 90-120 minutes, and then people have a short period of REM sleep.⁶ This cycle then repeats throughout the night. The four stages of sleep can be described as:⁵

  • Stage 1 NREM: The first stage of sleep consists of light sleep, and it’s when the body shifts from wakefulness to sleep. This stage lasts only a few minutes, and brain activity, heart rate, breathing rate, and eye movements begin to slow down. 

  • Stage 2 NREM: The next stage of sleep is the longest of all of the stages. During this stage, the body starts to move into deep sleep. Physical changes that occur during this stage include relaxation of muscles and a further decrease in heart rate, breathing rate, and brain waves. Additionally, eye movements stop and temperature decreases. 

  • Stage 3 NREM: This stage is where deep sleep, also known as slow-wave sleep, occurs. Your heart rate, breathing rate, and brain activity levels are at their lowest, and the muscles are the most relaxed. As you sleep throughout the night, the time spent in this stage decreases. 

  • REM: The last stage of sleep consists of slow-wave sleep, and it occurs about 90 minutes after falling asleep. It makes up about 20 to 25% of total sleep time in adults, and the time spent in this stage increases throughout the night. During REM sleep, the eyes quickly move beneath the eyelids, and heart rate and breathing rate increases. If you have dreams throughout the night, they occur in this stage. Interestingly enough, your muscles transition into a state of paralysis, which is likely meant to keep you from physically acting out your dreams. Lastly, this stage is where long-term memories are created.

Diagram of the four stages of sleep by The Dana Foundation.

On average, the body will complete this cycle four to five times a night.⁷ The total time the body spends in REM sleep decreases as age increases. Not only does age play a big role in the sleep cycle, but it also determines how much sleep the body needs to optimally function. 

How Much Sleep Do We Need?

The amount of sleep we need depends on several factors, with the most important one being age. Our sleep requirements are the highest when we’re first born, and they decrease as we age.

The National Sleep Foundation, the American Academy of Sleep Medicine, and the Sleep Research Society all recommend that those aged 18 years of age and above sleep a minimum of 7 hours each night.¹ Ideally those aged 18 to 64 years of age should get seven to nine hours of sleep, and those 65 years of age and older should aim to get seven to eight hours of sleep. However, those that are younger have different sleep requirements:⁵

  • 0-3 months of age: 14-17 hours

  • 4-11 months of age: 12-15 hours

  • 1-2 years of age: 11-14 hours

  • 3-5 years of age: 10-13 hours

  • 6-13 years of age: 9-11 hours

  • 14-17 years of age: 8-10 hours

When these sleep requirements aren’t met, the body suffers from sleep deprivation - something that has both short-term and long-term adverse effects.

What Are the Long-Term Effects of Sleep Deprivation?

Sleep deprivation occurs when you don’t get enough sleep. If you’re an otherwise healthy adult and get less than the recommended amount of sleep for several nights in a row, you may experience:⁸

  • Increased stress response

  • Pain within the body, such as headaches and joint pain

  • Reduced quality of life

  • Emotional distress

  • Mood disorders like anxiety and depression

  • Difficulty concentrating

  • Problems with memory

Because these symptoms occur when there is short-term sleep deprivation, they typically resolve once you’re able to get an adequate amount of sleep. However, if sleep deprivation occurs frequently and for a long period of time, there can be long-term adverse effects. These can include an increased risk of having:⁸

  • Obesity

  • Metabolic syndrome

  • Type 2 diabetes

  • High blood pressure

  • High cholesterol

  • Heart disease

  • Stroke 

  • Cognitive and memory disorders

  • Mood disorders

  • Certain types of cancer

  • A shorter life expectancy, particularly in men

Sleep is a necessary part of life, and if sleep deprivation occurs frequently, it causes harm to the body. Fortunately, there are many ways to improve your quantity and quality of sleep. 

How Can Sleep Be Improved?

Taking steps to improve the quality and quantity of your sleep can result in significant health benefits. Many people struggle with poor sleep because they have a hard time either falling asleep, staying asleep, or both. These struggles are typically a result of issues with the body’s circadian rhythm. It functions like an “internal clock,” and it’s how your body knows when to wake up and when to fall asleep. 

Research has found that there are ways to influence the circadian rhythm by making adjustments to lightness, darkness, temperature, food, exercise, and caffeine intake at certain times of the day. There are also certain supplements that have been shown to improve sleep. I’ll be reviewing some of these steps you can take to improve your sleep in my next blog. 

In the meantime, just concentrating your intentions about wanting to have more dreams and better sleep is a good place to start. 

I took a class in undergrad from a visiting professor on Jungian dream analysis, and I recall that I wasn’t sure if I would be able to do much in the class because I couldn’t remember my dreams. On the first day of class she instructed us to ask our subconscious for more dreams, and she said they would come. 

Sure enough, she was right. 

It took a couple of weeks, but slowly I began to remember my dreams. I would then wake up and write them down. I think the more I focused on paying attention to my dreams, the more my sleep cycles responded back and provided me with the information that I was requesting. 

Prioritizing sleep and reaching your dream state will help support balance, health, and healing within your mind and body. 


Works cited:

1. 1 in 3 adults don’t get enough sleep – (cdc.gov)

2. Sleep deprivation: a mind-body approach – (nih.gov)

3. About sleep’s role in memory – (nih.gov) 

4. Antioxidant benefits of sleep – (sciencedaily.com)

5. Why Do We Need Sleep? – (sleepfoundation.org)

6. Overview of Sleep – (merckmanuals.com)

7. Understanding Sleep – (dana.org)

8. Short- and long-term health consequences of sleep disruption – (nih.gov)