Why is it Important to Sleep

Dr. C P Ravi Kumar

17 August 2026

Sleep

Introduction

Throughout our lives we experience various States of Consciousness. There are times when we are conscious and alert and there are other times when we are conscious but daydreaming and some other times when we are just asleep. These are different levels of awareness on a daily basis. This article contains information about sleep. And after reading this article the reader will know the various aspects of sleep like why do we sleep, what happens in our brain as we sleep?

I hope after reading this you start to care and respect sleep time. Back then around the 1950s people thought that sleep is a passive and dormant part of our lives. It was only several decades later that we understood that our brains are active when we sleep too. And that sleep is important and essential for our physical and mental health. (American Sleep Association).

We are just beginning to understand many more aspects of sleep in the realm of psychology.

What is sleep?

Sleep is a state of consciousness characterised by lower physical activity and reduced alertness. is a state opposite to the wakefulness state where the person has increased physical activity and increased sensory awareness. One remarkable feature of sleep is that this state has certain brain patterns and these can be visualized using an EEG (Electroencephalography). There are different stages of sleep.

We are living organisms that regulate our internal state according to the outside environment and the world around us. This process is called Homeostasis. We have many internal rhythms that help us maintain this balance between the two worlds (Inside the body and outside). One such rhythm is the Circadian rhythm. This is our internal biological clock that regulates our sleep-wake cycle repeatedly on a daily basis. This pattern is attuned naturally to the rotation of the Earth around its own axis marking a completion of a day (~24 hours). The Sun should not be forgotten while we speak about sleep.

The Sun is the master of sorts because it is his light and temperature that drives the circadian cycle in us. And hence warm temperatures and bright light are associated with alertness/wakefulness and cooler temperatures and dim light is associated with sleepiness.

Sleep is a dynamic activity. This is controlled by certain neurotransmitters in different groups of nerve cells/neurons. The neurons at the base of the brain actually begin to start inhibiting or ‘switching off’ the signals that keep us awake. Chemicals like adenosine accumulate in our blood during wakefulness this build of adenosine causes drowsiness. And while we sleep this chemical is broken down and cleared. (American Sleep Association).

Having a healthy sleep routine helps maintain a healthy body weight, lowers stress levels, improves overall mood and increases motor coordination and many other benefits related to cognition and memory formation.

Why do we sleep?

We know that sleep is extremely important for an individual’s wellbeing. But scientists are still not sure about Why we need sleep? There are many reasonable hypotheses and theories proposed to answer this question. For me personally when I read all these reasons I felt that we sleep for all the given reasons because each of these theories are equally plausible.

The Evolutionary Theory

This theory is also known as the adaptive theory of sleep. Evolutionary Psychology studies the universal patterns of behavior and cognition that have evolved evolutionarily as a result of natural selection pressures. They say that sleep is essential to conserve energy and to restore all the resources that we spent during the day. They use the analogy of how a bear hibernates in the winter to conserve heat and resources when the bear’s food source is really scarce during the cold winter. Perhaps, we too sleep to conserve energy and reduce our energy expenditure.

But there is very little research that supports this explanation of why we sleep. According to some research there was found to be negative correlation between energetic demands and the time spent sleeping. (Capellini, Barton, McNamara, Preston, & Nunn, 2008 qtd in ‘States of Consciousness’, chapter 4) this theory says that we evolved sleep patterns as an adaptation to keep away from the risk of predators.

Hence our ancestors would sleep in safe areas which would reduce the risks of being spotted by predators. But research and comparative study shows that this relationship between predatory risk and sleep is quite complex and ambiguous. According to research, species that face a higher risk of predation sleep fewer hours than those species that do not have such a risk. Lions and bears sleep for about 12-15 hours a day but their prey gets no more than 4-5 hours of sleep. (Ezenwanne E. 2011 qtd in Cherry K., Jan 21 2020). This is actually a huge difference.

It is also possible that sleep serves not only one universal function; it can just be that different species have different sleep patterns that have evolved over time as a response to their various evolutionary pressures.

Information consolidation theory

This theory is based on cognitive research. The theory says that sleep helps to process information that we have acquired during the day. And it also helps the brain prepare for the next day. 2012 research done shows that sleep helps to cement information and push it to the long term storage. I watched a Ted Talk by Matt Walker, he experimented with two groups. One group had a full 8 hour sleep time whereas the other group members did not sleep at all.

The next day all the participants were given a list of facts to learn while inside an MRI scanner which took snapshots of the brain activity. He noticed that the group that was sleep deprived showed a 40% deficit in the ability for their brain to make new information without sleep. (Walker M. “Sleep is your superpower”, 2009). From this we know that sleep deprivation slows down learning and disrupts memory.

This leads to impairments in maintaining attention, decision making and to make new long term memory. (Brown. 2012 qtd in ‘States of Consciousness, chapter 4) after reading this students must realize that cramming all the information the night before the exam is not a very productive way of studying or learning.

The Clean Up theory/ Repair and Restoration theory

This theory suggests that sleep is the time when the brain cleans itself. The Mouse study done in October of 2013 showed that the brain removes toxins that were produced during the day. Brain cells produce byproducts (chemicals) during their normal activity and these have to be flushed out or broken down. When we sleep the fluid flow through the brain increases. This cleanses the brain of these waste byproducts and hence acts as the brain’s waste disposal system.

Problems with timely cleaning and removing of toxic waste might play a role in many brain disorders like Alzheimer’s disease. (Xie L, Kang H, xuQ et al.” Sleep drives metabolite clearance from the adult brain” qtd in ‘States of Consciousness, chapter 4) Sleep is essential even to restore all the physiological processes that keep us fit and healthy. During different stages of sleep our brain has different activities.

In the Non rapid Eye Movement [NREM] sleep the brain restores all the physiological functions, while in the Rapid Eye Movement [REM] phase the brain restores the mental functions. During sleep there is also an increased rate of cell division and protein synthesis. And hence it is suggested that repair and restoration activities also occur during sleep.

We also need sleep to survive

Studies done on animals show that sleep is a necessary condition for survival. The normal lifespan of rats is two-three years. Those rats that are deprived of REM sleep survive only for 5 weeks and rats that are deprived of all the sleep stages live only for 3 weeks.

These rats that are sleep deprived also develop very low body temperatures and sores on their paws and tails. They reasoned that the rats immune system was significantly damaged. (American Sleep Association).

To keep us growing [especially in children]

Deep sleep in children and young adults helps in the release of growth hormones. Since we have already read that the rate of cell division and protein production increases and since proteins are building blocks needed for cell growth and they help enhance repair damage from stress and UV rays. Certain nerve signals and pathways are repeated during sleep which suggests that repetition may improve learning and memory consolidation. Deep sleep is truly essential. (American Sleep Association)

How much sleep do we need?

The amount of sleep depends on our age and it varies from person to person.

According to the National Sleep Foundation adults need a maximum of seven to nine hours of sleep on a daily basis (American Psychiatric Association, August 2020). Infants require about 16 hours of sleep a day, teenagers need about 9 hours on average. But it is observed that some adults can be healthy and active with a mere five hours of sleep and some other adults need as much as 10 hours of sleep every night. These cases are exceptions because they are genetic.

Pregnant women need several more hours of sleep than usual during the first three months. As people get older they tend to sleep more lightly and for shorter time periods. Many people above the age of 65 have sleeping problems like insomnia frequently. As we grow older the deep sleep stages become very short or are completely lost.

This is considered as a normal process of ageing. When we don’t get proper sleep for many days we accumulate a ‘sleep debt’. (American Sleep Association) And our body will want that debt to be repaid. This will affect our reaction time and impair other cognitive and motor functions.

Many people take sleep time for granted and exploit the time for other purposes. It is reported that nearly 30% of adults sleep for 6 hours or so every night. And 30% of high school students get an average of at least 7 hours on a school night. (American Psychiatric Association, August 2020).

This information is again from a study done on American participants in America. But we can slowly notice the shifts in bed time here in India too. We can relate well to that study too.

The Circadian Rhythm

As we are already familiar with the fact that we have an internal rhythm that keeps us homeostatically attuned and regulated according to the outside environment. Now what do you think is the base for this function? Is it the heart? It is our brain that is responsible for this fascinating function. We call this rhythm the ‘Circadian rhythm’.

Circadian in Latin stands for “Around a day”. This rhythm is controlled by our internal clock. This clock is the Suprachiasmatic Nucleus [SCN]. It is a pair of small pin head sized brain structures that contain about 20,000 neurons. The SCN is found in the Hypothalamus just above the pituitary gland.

When light hits our eyes the photoreceptors in our retina signal the light to travel along the optic nerve to the SCN in the Hypothalamus. SCN further signals to many other areas of the brain regions like the Pineal gland. The pineal gland responds to the light induced signal and inhibits the secretion and production of Melatonin. Melatonin is produced when there is darkness and hence making us feel drowsy. The SCN is also responsible for regulating our body temperature, secretion of hormone, production of urine and blood pressure change as we sleep. (American Sleep Association).

Our Circadian rhythm can be affected by extra light (artificial lights) at night time. Many of us who use smartphones, laptops or watch TV screens at night are directly affecting our sleep by inhibiting the production of Melatonin, the sleep hormone. When people travel from one time zone to another they have a disruption in the circadian rhythm.

This uncomfortable feeling is known as “Jet lag”. This may take a couple of days for our internal clock to adjust to these abrupt changes.

This feeling is also experienced by those who work Night shifts. People who work night shifts are prone to seep disorders like insomnia. They have high risks of heart problems, disturbances in their digestive system, mental and emotional problems. (American Sleep Association).

Sleep Disorders

Almost all of us experience some of the symptoms of sleep disorders at some point in our life. But sleep disorders can really be dangerous for our physical and mental health in the long run. Appropriate diagnosis will help cure these disorders. Until now doctors have identified over 70 sleep disorders. Some of the most common disorders include insomnia, Parasomnias, sleep apnea and narcolepsy.

Here I will be discussing only these most common sleep disorders

Insomnia

Is the experience of consistent difficulty in falling or staying asleep. Insomnia is the most common type of sleep disorder. You need to seek help if the condition prolongs for two to three days a week for a whole month. (Roth, 2007 qtd in States of Consciousness, chapter 4). When we have difficulty falling asleep we tend to get anxious about it. The more anxious we feel the more aroused we are and all the more less likely to fall asleep.

These can go on to make you feel depressed and anxious. Mostly some forms of psychotherapy like cognitive behavioural therapy are used to diagnose this condition. This treatment would include appropriate management of stress and work towards changing problematic behaviours that keep the person from falling asleep.

Parasomnias

This includes a group of disorders where the person has unwanted/disruptive motor activity. Parasomnia can either occur in REM or NREM stages of sleep. This includes sleep walking, night terrors and restless leg syndrome. (Schenck, 2000 qtd in States of Consciousness, chapter 4). These are to be diagnosed as well. Because they too can cause unwanted misery and troubles. There is an instance when a man murdered his wife by stabbing her 44 times.

All this happened when he was asleep and was not conscious or aware of what he was doing. He was sleepwalking. (Cartwright, 2004; CNN, 1999 qtd in States of Consciousness, chapter 4) This sounds scary and bizarre but it can happen and is plausible if one has such a disorder.

Apnea

This condition is when the person’s breathing stops and this can last for 10-20 seconds. Sleep apnea is more common in overweight individuals and is often accompanied by snoring. This condition increases the risk of cardiovascular diseases. Sleep apnea has two types: obstructive sleep apnea and central sleep apnea. In Obstructive sleep apnea the person’s air passage is blocked and air is blocked from reaching the lungs.

In central sleep apnea signals from the brain that are responsible for regulating breathing are interrupted and hence the person gasps for breath. One of the most common treatments used is a continuous positive airway pressure (CPAP). This device has a mask that fits onto the person’s nose and is connected to a pump that pumps air forcing air into the passageway and hence ensuring that the pathway is open.

Narcolepsy

A person with Narcolepsy cannot resist sleep and hence falls asleep at inappropriate times. This is also accompanied by cataplexy where the person is unable to move his muscles or they feel weak. And sometimes the voluntary muscles are completely paralysed similar to the paralysis of the muscles in the REM stage of sleep in healthy individuals. Around one third of people having narcolepsy recall that they have vivid dreams during these periods (Chokroverty, 2010 qtd in States of Consciousness, chapter 4).

Narcolepsy is generally treated using psychomotor stimulant drugs.

Conclusion

Sleep deprivation slows down learning and memory.
When we sleep, fluid flow through the brain increases, removing all the toxic byproducts and reducing the risk for Alzheimer’s disease.
Sleep apnea increases the risk of cardiovascular diseases.
Sleep deprivation leads to increased irritability, mood swings, depression.
Sleep deprivation leads to cognitive impairment, memory isssues.

As sleep research becomes more popular and famous. Scientists are curious to get solutions for many questions associated with this active and dynamic state. They are working towards understanding the brain more holistically and how different regions function during sleep. This understanding would help us understand and treat sleep disorders and other related mental health problems better. It would truly help us have a good night’s sleep.

As Matt Walker in his talk says that sleep is our superpower and it is the only elixir that takes us near immortality.

So let us make the best out of this beautiful and fantastic state of being “SLEEP”. Goodnight!

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