Written by Ashima Yadav

Last Updated June 13, 2024

Marwa Ismail Fact checked by Marwa Ismail

Who doesn't enjoy sleeping in a little longer on a Sunday morning or putting off their alarm a little longer on a Monday morning? We, as humans, spend one-third of our lives sleeping. However, when it comes to knowing about it, we don’t seem to know much. This article explores the topic of sleep in detail, going over its mechanism, importance, stages, effects on health, related healthy habits, and disorders.

Key Takeaways:

  • Circadian rhythms and sleep-wake homeostasis are two mechanisms that regulate our sleep cycle.
  • There are 4 stages of sleep that one goes through, out of which three are non REM sleep and one is REM sleep.
  • Sleep has a significant effect on our mental and physical health.
  • Sleep duration and sleep health are two distinct concepts: sleep duration is the amount of time slept, while sleep health is the quality of sleep.
  • One can follow hygiene practices like setting up a sleep schedule, having a nighttime routine, creating a sleep conducive environment, etc. to improve sleep quality.
  • There are various sleep disorders that one might have, which should be identified and treated for better sleep as well as overall health.

The Mechanism Behind Falling Asleep

Sleep may just seem like a rest for the body after a tiring day. But it is much more than that. It is an essential, just like food and water. Our brain stays active throughout sleep and performs various functions that help with things like memory consolidation, toxin removal, and much more.

Let's take a closer look at the biological processes that help us control our sleep patterns before discussing the benefits of sleep and other sleep-related topics. We will better understand the remaining subtopics if we understand the sleep mechanism.

Circadian rhythms and sleep-wake homeostasis are two mechanisms that regulate our sleep cycle. These two biological processes work together to manage when we are asleep and awake.

sleep mechanism

Circadian Rhythm

Circadian rhythms are 24-hour cycles in our body. These cycles work in the background to maintain and regulate essential processes like metabolism, hormone secretion, body temperature, and, most importantly, the sleep-wake cycle. All these processes are maintained by different circadian rhythms throughout the body.

In the context of sleep, the circadian rhythm takes clues from our environment to determine the time for sleep. The most important cue is taken in terms of the light in your surroundings. When it gets dark, the circadian rhythms take a cue and release melatonin, the hormone that promotes sleep, which makes us feel sleepy at night.

Sleep-Wake Homeostasis

Sometimes also known as homeostatic sleep drive or sleep-wake cycle, sleep-wake homeostasis is an internal mechanism that keeps track of your sleep. It reminds the body to go to sleep after a certain period of wakefulness. The body’s drive to sleep increases along with the duration of the period of wakefulness and decreases when one sleeps. This sleep drive is also affected by other factors like medical conditions, mental health, medications, stress, etc.

Stages of Sleep

Now that we know the mechanisms behind sleep, let’s look at what happens during sleep. One goes through two types of sleep: Non-REM (Rapid-Eye Movement) sleep and REM sleep. The non-REM sleep consists of 3 stages, and REM sleep consists of 1 stage. These stages are discussed here in detail:

  • Stage 1: This stage is the transition from wakefulness to sleep. It is a small stage, lasting for about 5% of sleep. Your brain activity, heartbeat, eye movements, and breathing slow down. Your body relaxes, and there is an occasional twitch in muscles. Moreover, the brain stays relatively active and produces high amplitude (high voltage but low in frequency, 3.5-4.5 Hz) theta waves, which are slow brain waves occurring primarily in the brain’s frontal lobe.
  • Stage 2: This is a light sleep stage that lasts for about 45% of sleep, making it the longest period. During this stage, one's awareness level reduces, body temperature drops, eye movements stop, and breathing and heart rate become more regular. This stage is characterized by bursts of rapid and rhythmic brain wave activity, referred to as sleep spindles (12-14 HZ). These spindles occur 2 to 5 times per minute. These spindles are said to be a feature of memory consolidation.
  • Stage 3: This is a deep sleep stage that lasts for about 25% of sleep. During this stage, one's muscles relax entirely, blood pressure drops, breathing slows, and you progress into your deepest sleep. Your body also starts its physical repairs during this stage. As a result, having adequate restful sleep enables you to wake up feeling rejuvenated. The deep, slow brain waves, known as delta waves, are another feature of this sleep.
  • Stage 4: About 25% of (stage 3) sleep later, REM sleep begins. Your body becomes relaxed and immobile, breathing becomes rapid, eyes move quickly, and the majority of people dream during this stage. Your voluntary muscles become immobile during REM sleep, which prevents you from acting out your dreams while your brain is stimulated with mental processes.

Now that we know of the 4 stages we pass through during our sleep, it is also essential to know that one doesn’t necessarily pass through all these stages in the same order during the entirety of sleep. A complete sleep cycle lasts approximately 90-120 minutes. Therefore, one may go through 4 - 5 sleep cycles per night if they get the recommended amount of sleep.

Effects of Sleep on Mental and Physical Health

Since we spend one-third of our lives sleeping, it must affect us in some way or another. Have you ever noticed how you get irritated when you don’t get enough sleep? Well, it’s because sleep is a very important physiological activity, and it affects both our mental and physical health.

Importance of sleep for mental health

Sleep theories suggest that sleep plays a role in essential functions such as memory consolidation, information processing, emotional regulation, and cognitive functioning. A lack of sleep could disrupt these functions. So let’s take a deeper look at how sleep affects these functions.

Memory consolidation: Memory consolidation refers to the process of organizing newly acquired information and integrating it into long-term memory. When awake, we acquire a lot of new information daily, which is consolidated during sleep. During sleep, our brain goes through unique brainwaves linked to memory consolidation. Moreover, during the waking state, the limited neural resources have many functions to perform, which might make memory acquisition and consolidation incompatible processes. Whereas during sleep, there is a reduced activity of external stimulation, which gives the brain the opportunity for memory consolidation.

Emotional regulation: The control of emotions and stress is greatly aided by sleep. Sleep research has shown that the limbic system, the region of the brain responsible for emotions, is quite active during certain stages of sleep, especially when one is dreaming. Some dreams cause us to feel extreme emotions; you must have experienced such dreams at least once, be it a bad dream that scared you or a pleasant dream that made you wake up with a smile on your face. Researchers believe that such dreams help us with emotional regulation and integrating emotions.

Cognitive functioning: Sleep is crucial for our cognitive processes to function optimally. Even slight sleep deprivation can affect cognitive processes like attention, decision-making, memory, language, etc. Researchers have shown that sleep facilitates learning and memory, two very important components of cognition. The synaptic homeostasis hypothesis states that during sleep, synaptic connections go through a process called depotentiation, which is nothing but a reduction in the strength of these connections. However, according to this theory, some connections are protected from this depotentiation and become stronger. This suggests that during sleep, our brain works actively to strengthen the more important connections in the brain.

Importance of sleep for physical health

Have you ever felt easily fatigued after a sleepless night? This is because sleep has a restorative effect on the body. During sleep, our body conserves energy and utilizes it to repair and regenerate cells, tissues, and muscles. Let’s take a deeper look at how sleep impacts our physical health in different aspects.

Immune system function: The immune system benefits greatly from sleep. Studies have shown that sleep promotes the production of cytokines, T-cells, and natural killer cells. Cytokines are immune system activators and act as a defense against infections and diseases, while T-cells and natural killer cells are responsible for identifying and eliminating pathogens. Sleep helps the immune system function by promoting the production of these cells.

Cardiovascular health: Sleep is essential to cardiac functions and heart health. Sleep helps regulate blood pressure and heart rate. During sleep, our parasympathetic nervous system takes over, and blood pressure and heart rate decrease significantly. This pacing down allows these systems to rest and recover. Sleep disruption can also disrupt these systems’ regulation, putting the person at risk for cardiovascular problems. Moreover, sleep helps reduce stress, both physiological and psychological. Stress activates the sympathetic nervous system, leading to high blood pressure and heart rate, which is bad for health. The reduction of stress during sleep also keeps that risk at bay. Furthermore, with quality sleep, cholesterol levels are kept in check. Sleep disruption can cause an alteration in lipid metabolism, leading to increased cholesterol, which can, in turn, cause cardiovascular disease.

Hormonal regulation: Sleep is associated with the production and reduction of many hormones, which helps us maintain hormonal homeostasis. For instance, sleep reduces the production of cortisol, which is a stress hormone. Sleep deprivation causes a rise in cortisol, which leads to excessive stress. On the other hand, GH, or Growth Hormone, production is increased during sleep, which helps in muscle growth. Sleep also plays a role in other hormonal secretions like metabolic hormones, insulin, and thyroid-stimulating hormones. Disruption of sleep patterns can disrupt the balance of these hormones and create problems in day-to-day life.

Sleep Duration and Sleep Health

Sleep duration and sleep health are closely related but distinct concepts. Sleep duration, or sleep hours, refers to the amount of time a person spends sleeping, while sleep health refers to the quality of sleep. A sufficient amount of sleep is necessary, but if sleep quality is disrupted, one won’t have restful sleep. Let’s look at sleep hygiene practices one can follow to maintain healthy sleep and the benefits of following hygiene practices.

Sleep hygiene practices

Sleep hygiene is nothing but healthy sleep habits. Practicing hygiene is a great way to improve your sleep quality. By now, we are well aware of the effects of sleep on our physical and mental health; we know that any sleep disruptions can cause the quality of our lives to drop. Therefore, practicing good sleep hygiene practices is essential to getting some quality sleep. Below are some healthy sleep habits that you can follow:

  • Setting up a sleep schedule: Setting up a sleep schedule can help make your body and mind accustomed to sleeping at the same time every day, making it easier to fall asleep. Having a fixed sleep time regardless of weekends, work, or study can immensely help with sleep quality. 
  • Establishing a bedtime routine: Having a bedtime routine can help your body and mind unwind and get ready to sleep. Having a consistent nighttime sleep routine can also help you fall asleep more quickly. Your bedtime routine can include anything that helps you relax and gives you comfort. Taking a shower, reading a book, meditating, or doing breathing exercises are a few common things that can help you relax.
  • Sleep environment: Your bedroom environment also affects sleep quality, so having a sleep-conducive environment is a must. Switching off bright lights, having comfortable bedding, turning off all the distracting electronics, and keeping your blue light devices away can make your bedroom a better place for sleeping and provide you with a good night’s sleep.
  • Avoiding stimulants before bedtime: Consuming stimulants like caffeine, nicotine, or alcohol late during the day can disrupt your sleep. These stimulants interfere with the sleep cycle and sleep quality. So one should avoid consuming these anytime before bedtime.

Sleep Disorders

Now that we are well aware of how sleep works and how important it is, it’s also beneficial to be aware of sleep-related disorders. If you constantly have sleep-related issues, even after following sleep hygiene practices, you might have some sleep disorders. In this section, we discuss some major sleep disorders and their symptoms. However, if you think you might have a sleep disorder, it’s best to consult your doctor.

Insomnia: Insomnia is one of the most common disorders. Around 30-40% of adults in the US reported having insomnia symptoms at some point. Insomnia is characterized by trouble falling asleep, staying asleep, or both. Insomnia can be acute or chronic. Acute insomnia is when a person faces symptoms for a short period due to life’s situational stresses. In comparison, it is characterized as chronic if one has the symptoms at least thrice a week for a month or longer. It can occur by itself or be related to some other underlying health condition. It can result in poor sleep quality, insufficient sleep, missed sleep, and other sleep problems. It can cause various issues in daily life, including decreased productivity, tiredness, fatigue, distress, and other cognitive functions like attention, memory, etc. A common treatment for insomnia includes cognitive-behavioral therapy and the use of sleep medicine.

Sleep Apnea: Sleep apnea is when one experiences interrupted breathing during sleep. It can be of two types: obstructive or central. In obstructive sleep apnea, the throat muscle relaxes, leading to airway blockage, while in central sleep apnea, the brain stops sending signals for breathing to the responsible muscles. People with this condition experience snoring and may wake up from sleep gasping for air. If left untreated, it can have serious consequences. If you suspect you might have it, consider visiting your doctor.

Parasomnias: Parasomnias are a class of disorders wherein one experiences abnormal sleep behaviors like sleepwalking, sleep eating, bed wetting, and sleep terrors, among others. While parasomnia is more common in children, adults can also experience it. These behaviors cause sleep disturbances, prevent one from getting restful sleep, and lead to poor sleep. It may also cause harm to the person experiencing it or others around them.

Narcolepsy: Narcolepsy is a neurological condition that affects one’s ability to regulate sleep-wake cycles. People with narcolepsy feel excessive daytime sleepiness and may experience sleep attacks and sudden episodes of falling asleep during the day. These sleep attacks may be accompanied by cataplexy, a sudden loss of muscle tone. If left untreated, it can be dangerous for the person experiencing it and others around them.

Circadian rhythm sleep-wake disorders: Circadian rhythm disorders occur due to misalignment between your body’s internal cues and your environment or desired time to sleep. Sleep disruption due to jet lag is a typical example of a circadian rhythm disorder. There are various types of circadian rhythm disorders. They can be treated with hormone melatonin supplements, light exposure, or other lifestyle changes as per the type of disorder one might have.

Restless Leg Syndrome (RLS): Restless leg syndrome is a disorder characterized by an irresistible urge to move legs, along with aches, tingling, or burning sensations in the leg. During an episode of RLS, moving your legs around or taking a walk provides temporary relief. RLS can occur at any time, but mainly it occurs late in the evening or while one is resting, trying to sleep, or sleeping. It may cause trouble sleeping or disrupt sleep, resulting in a lack of quality sleep. Depending on the cause of RLS, it may be treated with iron supplements, weight loss, or other medications.


In conclusion, sleep holds immense significance in our lives, influencing virtually every aspect of our well-being. By understanding more about sleep, we gain insight into our own sleeping habits and can make adjustments to enhance the quality of our sleep and, consequently, improve our overall quality of life. Throughout this article, we delved into various facets of sleep and its profound effects. It is our hope that this exploration has offered you a fresh perspective on sleep or, at the very least, expanded your knowledge on the subject.

Disclaimer: What is said in this article has been referenced from multiple sources and is intended only for educational and informational purposes. Please note that no content in this article is a substitute for professional advice from a qualified doctor or healthcare provider. Always consult an experienced doctor with any concerns you may have regarding a health condition or treatment, and never disregard any medical suggestions or delay in seeking treatment because of something you read here.