Sleep: The Science, Stages and Its Importance To A Quality Life

Sleep is a natural part of our daily lives. It is activity that all living creatures engage in. Proper sleep enables us to function at our optimal level and lead a quality life. Yet, sleep deficiency is a global problem.

In this post I will be exploring the the science behind the sleep cycle, the stages of sleep, and why sleep is important for a quality life.

The Science of Sleep

The sleep cycle is governed by an internal clock that runs on a 24-hour cycle called the circadian rhythm. Two processes help to control this rhythm: adenosine and light exposure.

Adenosine is a compound produced in the brain. It is an inhibitory neurotransmitter that promotes sleep and suppresses arousal. During wakefulness, the amount of adenosine in the body increases. At night this compound is broken down by our body. Adenosine therefore regulates sleep homeostasis.

Light is an environmental factor that interacts with our internal clock to regulate sleep-wake cycle. When the eye perceives light, specific cells located in the hypothalamus signal the brain that it is daytime. Our body then produces cortisol which encourages alertness and provides us with energy.

As daylight fades and night approaches, our body produces a hormone called melatonin. This hormone promotes drowsiness and signals our body that is time to prepare for sleep. Therefore, harsh light from our devices can interfere with melatonin production and disrupt our sleep cycle.

The Sleep Stage

There are four stages of sleep broken into two types: non-REM, non-rapid eye movement and REM, rapid eye movement. The first three stages follow under non-REM.

non-REM sleep

  1. This is the transition stage of sleep. You have fallen into a light sleep. Your body is relaxed and your heart rate, breathing and eye movements have slowed down. This lasts only a few minutes.
  2. You are in a deeper sleep. Your heart and breathing is even slower, your muscles are more relaxed and brain waves are low. Eye movement has stopped and your body temperature is low. This is the longest stage.
  3. At this point every thing is fully relaxed and activity is at its lowest and slowest. This stage duration decreases throughout the night.

REM sleep

In this stage eye movements are back and your heart rate, breathing and blood pressure begins to rise. At this point you begin to dream and your limbs are paralysed to prevent you from acting out dreams. As the night goes on the duration of this stage increases.

The entire cycle takes about 90 to 120 minutes. On average we need to go through 5 of these cycles for optimal benefits. Therefore, aim for approximately 7 hours and 30 minutes of sleep per night. However, please note that the rhythm and timing of this cycle changes with age. Kids require longer hours to for growth and development, thus this timing decreases with age.

Sleep Recommendations

Below are the approximate hours of sleep per stage of development according to the CDC:

StageAge rangeHours of sleep
New-borns0-3 months14-17 hours
Infants4-12 months12-16 hours
Toddler1-2 years11-14 hours
Pre-school3-5 years10-13 hours
School-age6-12 years9-12 hours
Teen13-18 years8-10 hours
Adult18-60 years7-plus hours
Adult61-64 years7-9 hours
Adult65+ years7-8 hours
Derived from the CDC

Why Sleep Is Important

Getting the right about of quality sleep is vital to our well-being and quality of life. Below are 3 main reasons for getting proper sleep each night.

Brain Functioning and Emotional Well-Being

Lack of sleep can negatively impact your cognitive abilities and concentration. You are unable to focus enough to learn new skills because you are too tired. You are easily distracted and frustrated. Good night’s rest can help your brain store and retain information. Your memory will thank you for it.

When we are tired, we are more cranky and easily irritated. Our patience is short and tolerance level is low. This can make interactions tedious because our ability to regulate our emotions are diminished. Relationships can be hurt because of our sleep deficiency.

Physical Health

Tiredness saps our strength and stamina. We are less coordinated and energetic. Our bodies take longer to heal and recover from injuries or stress and our immune system weakens. As a result we are more susceptible to illness and diseases. Sleep deprivation affects our bodies ability to regulate our insulin level making us more at risk for diabetes. Poor sleep also affects our growth and development. During sleep our bodies repair cells and tissues and promotes muscle growth.


Lack of sleep can negatively impact your productivity. When you are tired you have less mental capacity to handle daily stressors, think clearly and focus on tasks and goal. You are easily distracted and your resolve is weaken. This can lead to more accidents which can be devastating. For the safety of yourself and other, get enough quality sleep each night.

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Thank you for reading.


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