Tag Archives: sleep

Why Do We Need to Sleep?

While not many may know why we need to sleep, most of us do know at some level that sleeping makes us recover the weariness from the previous day or days. Researchers have now shown that sleeping helps us retain information processed in the day time, restore and grow muscles, repair tissues, and even synthesize hormones. However, we still do not know the mechanisms behind much of these known effects of sleep.

A Question Unanswered?

For the past decades, scientist have explored this topic over several aspects. Despite this, it has been difficult to answer this question thoroughly with just one single theory. Instead, sleep patterns can be explained through several sleep theories.

Theories of Sleep

Inactivity theory

One of the earliest theories for sleep, which bases its idea from animal evolution theory.  The theory suggests that inactivity at night serves as a survival function that would keep them out of harms’ way. This is especially the case of animals who would rely heavily on their day time visions. These animals would avoid accidents from happening during night times, for example, trespassing into predatory zones. However, this does not explain why some vision-based animals or humans sleep during the day time.

Restorative Theories

A long held believe is that sleep in some way restores what is lost in the body while we were awake. Sleep provides an opportunity for our body to repair and rejuvenate itself. It is shown that for animals that are completely deprived of sleep loses all immune functions and die within a couple of weeks. This result further supports that some of the major restorative functions like the repair of muscles, protein synthesis, and growth hormone release only occur during sleep.

On its brain and cognitive aspect, the neurons in our brain produces a type of by-product in our brain called adenosine. The build up of these adenosine is thought to be one contributing factor for why we get tired and drowsy. This reaction in our brain is thought to promote the drowsiness while we are awake. When we sleep, our brain has a chance to clear the adenosine from our neuro-system; and when we have enough sleep and wake up, we would feel more alerted with low level of adenosine in the brain.

 Environmental-Cue Theory

This theory involves the internal clock of your body, where the body is in sync with certain cues in the environment. The different light intensities that you receive during day and night are the cues that makes you feel awake or drowsy.For example, light signals received through your eyes transmit a neuro signal to a special area of your brain that it is daytime. This area of the brain helps align your body clock with periods of the day and night. Your body releases chemicals in a daily rhythm, which your body clock controls. When it gets dark, your body releases a hormone called melatonin, which signals your body that it’s time to prepare for sleep, and it helps you feel drowsy. Exposure to bright artificial light (TV screen, computer screen, cell phone etc.) in the late evening can disrupt this process, making it hard to fall asleep. As the sun rises, your body releases a hormone called the cortisol, which naturally prepares your body to wake up.

source: Division of Sleep Medicine at Harvard Medical School

Recommended hours of sleep for each age group:

The amount of sleep you need each day will change over the course of your life, but irregular sleep habits and long-term sleep loss will affect your health in the long run. Certain medical conditions are associated with sleep disorder or deficiency . For example:

• high blood pressure
• attention-deficit hyperactivity disorder (ADHD)
• heart failure
• obesity

Hence, it is necessary to maintain a healthy sleep pattern.  Although sleep needs vary from person to person, the chart below shows general recommendations for different age groups:

source: National Sleep Foundation

The goal of learning sleep patterns is to better understand the importance of sleeps and enjoy its health benefits. Hope everyone can get enough sleep, because it is vital for us in the future. If you have any sleep theories that you would like to share or anything you just want to share, please comment below!

By: Robin Yuyang Wei