The Betterment Project

The Science Of Sleep: The Ultimate Guide

We need to sleep for about a third of every day or about an hour for every two hours we spend awake. The importance of sleep cannot be overstated. Sleep is as essential to our health and wellbeing as food and water, and most of us want the best sleep we can get.

When you devote eight hours to something, you expect results, but sometimes making time for sleep can be difficult. Also, waking up feeling rested or getting a good night’s sleep can be elusive. It feels like we’re forever researching how to master this essential part of our lives. 

So, why do we need sleep? What happens if we don’t get enough sleep? How do we get
a good night’s sleep? Let’s find out.

Why Do We Need Sleep?

We think of sleep as a time for resting or doing absolutely nothing, but the truth is our bodies are hard at work as we sleep. Under the calm surface of sleep, our bodies and minds are in a recovery mode. It is essential for our physical, emotional, and mental health.


Almost immediately after you fall asleep, your body and mind experience changes. Brain activity slows, the body’s core temperature drops, and the heart rate and respiration rate slow down. Because your body is at rest and the primary functions slow down, your body does not use a lot of energy while you’re sleeping.

The body goes through a full sleep cycle every 90 to 120 minutes during sleep, so on average, a person experiences roughly four complete sleep cycles during a night when they’re getting the recommended 8 hours of sleep. Each sleep cycle consists of four stages.

During each
stage of a sleep cycle, the body and mind have a different task in order to repair and reorder the body and mind for the next day. For example, during the second stage of a sleep cycle, your brain works to consolidate your memories from the day as it works to gather, filter, and process them. The film “Inside Out” by Disney Pixar captures this event wonderfully. 

Sleep Stages of the Sleep Cycle

N1 - Once you’ve fallen asleep, that limbo feeling is stage one or N1 of the sleep cycle. This is when you shift from wakefulness to sleep, and it consists of a period of light non-REM sleep.

This is when that first minute of sleep occurs and your heart rate, breathing, eye movements, and brain waves all slow down. Your muscles also relax, but they will also occasionally twitch. You will be in this stage of your sleep cycle for about five minutes or less. 

N2 - Your muscles will continue to relax and your eye movements will stop. This is the stage when your body temperature will drop. This is stage two or N2, and you are in a deeper non-REM sleep than the previous stage. N2 stage lasts about 25 minutes. As your sleep cycle continues throughout the night, the amount of time you spend in N2 grows longer. N2 is the stage of the sleep cycle where about 50 percent of sleep in adults takes place.


N3 - The third stage is also non-REM sleep, and it is called N3. This is where the deepest stage of our sleep cycle occurs. This stage is the hardest to wake up from. During N3 our heart rate, breathing, and brain waves are more regular. Unlike the previous stage, this stage gets shorter with each round of sleep cycles. So, you experience most of your deep sleep in the first half of the night. The amount of deep sleep we get at night tends to decrease with age. 

REM Sleep - REM sleep is the last stage in the sleep cycle. REM stands for rapid eye movement because the eyes move quickly from side to side during this sleep stage. During REM sleep, your breathing quickens and becomes less even. 

Your breathing is not the only thing to become less regular. Blood pressure and heart rate are more erratic unlike the previous stage. REM sleep gets credit for being the dream cycle, and it is in the stage that most people experience the muscle paralysis known as muscle atonia. Muscle atonia is what keeps us from acting out our dreams. 

The fourth stage lasts about 10 minutes during the first sleep cycle, and like N2, it increases in length as the night goes on. In the last cycle of sleep, the REM stage can last up to one hour. This can prompt the feeling that you’ve been dreaming all night. 

The mind and body need every stage in the sleep cycle to repair and recover from each day. For example, the brain requires REM sleep in order to enable key functions like memory and learning. When we have a restful sleep, we travel through our personal sleep cycles and spend quality time in each stage.

How Do We Sleep?

Our bodies will regulate our sleep in the same way it regulates other functions. The brain monitors the body and sends out instructions to keep the body in a normal state. Our bodies use two indicators to tell us when it is time to sleep.


The body’s sleep-wake homeostasis is the guiding principle that the longer we are awake, the more we feel the need to sleep. The pressure to sleep builds up in our bodies as we stay awake, similarly to how we feel the lactic acid build up in our bodies during a workout. This same pressure to sleep will also drive us into a longer, deeper sleep when we’ve not been getting enough rest lately.

Another way our body keeps our sleep regulated is through the natural 24-hour biological clock. This clock is called our circadian rhythm, and it plays an important role in a lot of the body’s processes. Our body uses our exposure to sunlight to keep our circadian rhythm in step. We feel the need to be awake during the daylight hours, and we start to feel the need for sleep at night after the sun has set.

In a perfect scenario, our body would sense that we had been awake long enough, the sun had set, and it was time for sleep. If you’ve ever had trouble sleeping or even staying asleep, you know that sometimes the body doesn’t get the message.

Different factors can cause us to fall out of rhythm or influence our sleep schedule. When we’re stressed, hungry, had too much caffeine, or had too much light exposure because we wouldn’t put down our phone, we can find it difficult to fall asleep when we know we need to be resting. 

What happens to our bodies when we don’t get adequate amounts of sleep?

Signs You Aren’t Getting Enough Sleep

There are times in our life that we just don’t get enough sleep. College students cramming for exams, parents with a newborn, anyone with a loved one in the hospital, shift workers, and most of us can all attest to the adverse effects that come from lack of sleep. When you go too long without sleep, sleep deprivation can take hold.

You can sleep every night, but you can still not be getting enough sleep. If you’re not sure if you’re sleep deprived, here are some signs that you need to schedule more sleep.


  • You are feeling especially moody.
  • You are noticing significant dips in your productivity and performance.
  • You are hungrier than usual and/or have unexplained weight gain.
  • You are having trouble with your skin.
  • You are having a hard time making decisions.
  • You are suddenly not into being intimate.
  • You are sleepy during the day.

These signs of sleep deprivation are bad enough, but if you have prolonged bouts of poor sleep quality, you can put yourself at increased risk for developing
mental and physical health problems such as:


  • High blood pressure
  • Metabolic health issues
  • Obesity
  • Mental health issues
  • Heart attack, heart issues
  • Stroke
  • Weight gain can stem from lack of sleep causing a poor appetite (foods with increased calories) by raising your levels of ghrelin, and lowering levels of leptin)
  • Slow reaction time
  • Higher levels of the stress hormone cortisol

If you haven’t been prioritizing sleep, use this as a wakeup call to get more shuteye. How can you make sure you’re getting enough rest?

How To Regularly Have a Good Night’s Sleep


To avoid sleep deprivation and to help your body find its rhythm again where you get plenty of sleep, you may need to adopt a policy of prioritizing your sleep. Here are some prevention steps, relaxation techniques, and lifestyle changes to make to ensure you have a healthy and applicable bedtime routine so you can not only get much sleep, but also the right sleep for your body.

1 - Sleep Starts In The Morning

Sleep starts in the morning? That doesn’t sound right, but starting your day with a little sunlight is a good way to reset your rhythm. Enjoying your morning beverage outside or taking a quick stroll in the morning light will help tell your brain that it’s time to be awake for the day. When your brain registers that the waking hours have begun, this will allow your sleep pressure to build up and get you sleepy on time at night.

2 - Make Time To Get Enough Sleep

For adults, it is recommended that you get 7 to 9 hours of sleep per night. Everyone has their own rhythm. Some people need less, and others need more. However, aiming for a number of hours that’s in that range will help you discover your magic number of hours. Whatever your body’s preference, the only way you’re going to avoid sleep deprivation is by making time for sleep. 

3 - Take a Sleep Supplement

If you struggle to fall asleep, stay asleep, or wake up feeling refreshed, you may need a little help. However, adding medications that can help you sleep, even over-the-counter medicines, can be addictive, leave you feeling groggy the next morning, or even be taxing on your body when you take them frequently. 

One of the best things about healthy sleep hygiene is that it means you’re in sync with the natural sleep-wake cycle. When you need help establishing that synchronization, you’ll want something natural. Thankfully, there are sleep supplements like
Complete Calm Sleep Gummies to achieve your sleep goals. 



Taking a gummy at night about a half hour to an hour before bed can be a tasty treat that can help you calm your mind and get you in the right mindset for falling asleep. Letting yourself get a good night’s sleep just might show you that it wasn’t the stress but the lack of rest that was keeping you feeling out of sorts.

4 - Keep It Cool

When the sun sets, the earth is cooler. Even in the deserts, the nights get chilly. Maybe that’s why our bodies respond to cooler temperatures as we sleep. We intuitively know that we sleep when it’s dark and cool outside. In our climate-controlled homes, it may help to set your thermostat to help you tune into your natural circadian rhythms. The recommended temperature for your bedroom as you sleep is around 65° F. By maintaining a
comfortable temperature with low light levels you can create a reliable setting to peacefully drift asleep.

5 - Turn Off Your Screens

A lot of us enjoy the guilty pleasure of scrolling through our phones or electronic devices while we’re in bed at the end of a long day or watching reruns of our favorite comfort show. Unfortunately, this screen time before bed is not helping us sleep, and it’s just confusing our brains. 

This confusion means that the hormones that our bodies release that tell us to wind down and go to sleep aren’t told to hit the field. So, we’re perpetuating our wakefulness and making ourselves oblivious to the sleep pressure our bodies have built up throughout the day. 

In the same way that you don’t want to hype up a child with sugary drinks and candy before bedtime, you don’t want to hype yourself up unintentionally with additional screen time. Take care of yourself by finding a new way to end the day like with a calming bath, relaxing music, or a few pages of a book.

Additional Tips

Be sure to limit large meals and alcohol consumption before bedtime. Although it can make people relaxed and drowsy, it suppresses the production of melatonin, which is the natural sleep hormone, causing a very disrupted sleep pattern while reducing your REM sleep.

Consider taking a warm bath, as it can help ease you into a relaxed state while preparing you for bed roughly 30 minutes to one hour before bedtime. 


is as important as air, food, and water to our survival. It plays a crucial role in the health of our body and especially our minds. Understanding the body’s need for sleep and how to get the best sleep you can is important to your sleep hygiene.

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Stages of Sleep | Sleep Foundation 

Sleep/Wake Cycles | Hopkins Medicine  

Best Temperature to Sleep: Research and Sleep Tips | Healthline

Extent and Health Consequences of Chronic Sleep Loss and Sleep Disorders | NCBI 

Meet our Experts

This article has been reviewed by members of our Scientific Advisory Board.

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