How Sleep Works: Sleep Phases and Stages

- By Lofta
How Sleep Works: Sleep Phases and Stages
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By Lofta
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This article explores the fascinating world of sleep, delving into its fundamentals, the different stages involved, and how sleep patterns change throughout life. It also highlights common sleep challenges and potential solutions, emphasizing the importance of healthy sleep for overall well-being.

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Sleep is essential for our health and well-being. It affects our mood, memory, learning, immunity, and more. But how does sleep work? What happens in our brain and body when we sleep? And what are the challenges that can disrupt our sleep quality and quantity?

In this article, we will explore the fascinating world of sleep, from the basics of sleep to the different phases and stages of sleep. We will also look at some common sleep challenges, such as sleep apnea, and how they can be treated with proper therapy. Finally, we will see how sleep changes with age and what we can do to optimize our sleep as we grow older.

The Basics of Sleep

Sleep is vital for our survival and well-being. It helps us to restore our energy, repair our tissues, consolidate our memories, regulate our emotions, and enhance our cognitive abilities. It is characterized by changes in brain wave patterns, eye movements, muscle tone, breathing, heart rate, and other physiological functions. Sleep also plays a key role in maintaining our circadian rhythms, which are the internal clocks that synchronize our biological processes with the 24-hour cycle of light and dark.

The Sleep Cycle: An Overview

One of the most important aspects of sleep is the sleep cycle. The sleep cycle is the sequence of stages that we go through during a typical night of sleep. A typical sleep cycle lasts about 90 minutes and repeats four to six times per night.

The sleep cycle consists of two main types of sleep: non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. NREM sleep is further divided into three stages: stage 1, stage 2, and stage 3, and REM sleep which is the stage where we experience vivid dreams.

NREM Sleep: The Foundation

NREM sleep is the type of sleep that prepares us for REM sleep. It is also known as slow-wave sleep or deep sleep because of its slow brain wave activity. NREM sleep is essential for physical recovery and mental health.

The stages of NREM sleep are:

  • Stage 1: This is the lightest stage of NREM sleep and the transition from wakefulness to deeper sleep. It lasts about 5 to 10 minutes and accounts for about 5% of total NREM time. In this stage, our brain waves are slow and irregular (theta waves), our muscles are relaxed but still active, and our eyes move slowly (rolling eye movements). We may experience hypnic jerks (sudden muscle twitches) or hypnagogic hallucinations (dream-like sensations) in this stage.
  • Stage 2: This is the intermediate stage of NREM sleep and the most prevalent stage of sleep. It lasts about 10 to 25 minutes and accounts for about 45% to 55% of total NREM time. In this stage, our brain waves are slower but show bursts of activity (sleep spindles) or sudden increases in amplitude (K-complexes). These brain waves help us to maintain a stable level of arousal and protect us from being disturbed by external stimuli. Our muscles are more relaxed but still responsive, and our eyes are still.
  • Stage 3: This is the deepest stage of NREM sleep and the most restorative stage of sleep. It lasts about 20 to 40 minutes and accounts for about 15% to 25% of total NREM time. In this stage, our brain waves are very slow and synchronized (delta waves), our muscles are very relaxed and unresponsive, and our eyes are still. This is the stage where our body repairs itself, strengthens its immune system, builds bones and muscles, and releases growth hormones.

REM Sleep: The Paradox

REM sleep is the type of sleep that is associated with dreaming. It is also known as paradoxical sleep because of its paradoxical nature. REM sleep is essential for emotional regulation and cognitive function.

The characteristics of REM sleep are:

- Brain wave activity: Our brain waves are fast and similar to those when we are awake (beta waves). However, our brain is more active in some regions than others, such as the limbic system (the emotional center) and the visual cortex (the visual center). Our brain also shows a high level of connectivity between different regions, which may facilitate memory consolidation and creativity.

- Muscle activity: Our muscles are paralyzed (atonia) except for those that control breathing and eye movements. This prevents us from acting out our dreams and injuring ourselves or others. However, some people may experience REM sleep behavior disorder (RBD), which is a condition where muscle paralysis is incomplete or absent, causing them to act out their dreams physically.

- Eye movement: Our eyes move rapidly in different directions (rapid eye movements or REMs). These eye movements are correlated with the content and intensity of our dreams. They may also help us to scan the visual images in our dreams or stimulate the visual cortex.

- Dreaming: We experience vivid and often bizarre dreams that may reflect our emotions, memories, fears, desires, or fantasies. We may also experience lucid dreams, which are dreams where we are aware that we are dreaming and can control or manipulate the dream content.

REM vs NREM: The Key Differences

REM and NREM sleep are both important for our health and well-being. However, they have different functions and characteristics. Here are some of the key differences between REM and NREM sleep:

  • Duration: REM sleep lasts about 10 to 60 minutes per cycle, while NREM sleep lasts about 70 to 80 minutes per cycle.
  • Frequency: REM sleep occurs about four to six times per night, while NREM sleep occurs about three to four times per night.
  • Timing: REM sleep occurs more frequently and longer in the second half of the night, while NREM sleep occurs more frequently and longer in the first half of the night.
  • Brain activity: REM sleep shows high brain activity in some regions but low activity in others, while NREM sleep shows low but uniform brain activity across regions.
  • Muscle activity: REM sleep shows muscle paralysis except for breathing and eye movements, while NREM sleep shows muscle relaxation but responsiveness.
  • Eye movement: REM sleep shows rapid eye movements in different directions, while NREM sleep shows slow or no eye movements.
  • Dreaming: REM sleep shows vivid and often bizarre dreams, while NREM sleep shows less frequent and less vivid dreams.

Sleep Challenges and Sleep Apnea

Sleep is essential for our health and well-being. However, many people face challenges that can affect their sleep quality. Some of these challenges are:

Insomnia: This is the difficulty falling asleep or staying asleep, resulting in insufficient or non-restorative sleep. Insomnia can be caused by various factors, such as stress, anxiety, depression, medical conditions, medications, lifestyle habits, or environmental factors. Insomnia can impair our physical and mental health, as well as our daily functioning.

Restless leg syndrome (RLS): This is a condition where we feel an uncomfortable sensation in our legs that urges us to move them. RLS usually occurs at night when we are trying to fall asleep or during periods of inactivity. RLS can be caused by various factors, such as genetic predisposition, iron deficiency, kidney disease, pregnancy, or medications. RLS can interfere with our ability to fall asleep or stay asleep, resulting in poor sleep quality and daytime fatigue.

Sleep apnea: This is a condition where we stop breathing repeatedly during sleep due to a blockage or collapse of the upper airway. Sleep apnea can be classified into two types: obstructive sleep apnea (OSA) and central sleep apnea (CSA). OSA is more common and occurs when the muscles in the back of the throat relax too much during sleep, causing the airway to narrow or close. CSA is less common and occurs when the brain fails to send signals to the muscles that control breathing during sleep.

Sleep apnea occurs when the muscles that control the airway relax too much during sleep, causing the airway to collapse or narrow. This reduces or stops the airflow into the lungs, resulting in low oxygen levels in the blood. The brain senses this drop in oxygen and sends a signal to wake up the person briefly to resume breathing. This cycle of interrupted breathing and arousal can happen hundreds of times per night, disrupting the normal sleep architecture and quality.

There are three main types of sleep apnea:

Obstructive sleep apnea (OSA): This is the most common type of sleep apnea, caused by a physical blockage of the airway by the soft tissues of the throat, such as the tongue, tonsils, uvula, or soft palate.

Central sleep apnea (CSA): This is a less common type of sleep apnea, caused by a failure of the brain to send signals to the muscles that control breathing.

Complex sleep apnea syndrome (CSAS): This is a rare type of sleep apnea, caused by a combination of both obstructive and central factors.

Symptoms and risks of sleep apnea

Sleep apnea can affect anyone, regardless of age, gender, or ethnicity. However, some factors can increase the risk of developing sleep apnea, such as:

  • Being overweight or obese
  • Having a large neck circumference
  • Having a narrow or crowded airway
  • Having enlarged tonsils or adenoids
  • Having a family history of sleep apnea
  • Smoking or drinking alcohol
  • Using sedatives or narcotics
  • Having certain medical conditions, such as diabetes, heart disease, stroke, etc.

The most common symptom of sleep apnea is loud and chronic snoring, often accompanied by gasping or choking sounds. However, not everyone who snores has sleep apnea, and not everyone who has sleep apnea snores. Other symptoms of sleep apnea include:

  • Excessive daytime sleepiness or fatigue
  • Difficulty concentrating or remembering
  • Irritability or mood changes
  • Headaches or dry mouth in the morning
  • Frequent urination at night
  • Decreased libido or impotence

Sleep apnea can have serious consequences for health and quality of life if left untreated. Sleep apnea can increase the risk of:

  • High blood pressure or hypertension
  • Heart attack or heart failure
  • Stroke or transient ischemic attack (TIA)
  • Irregular heartbeat or arrhythmia
  • Diabetes or insulin resistance
  • Depression or anxiety
  • Cognitive impairment or dementia

CPAP Therapy and Lofta

One of the most effective treatments for sleep apnea is continuous positive airway pressure (CPAP) therapy. CPAP therapy involves using a device that delivers pressurized air through a mask worn over the nose or mouth during sleep. The pressurized air acts as a splint to keep the airway open and prevent it from collapsing. CPAP therapy can improve breathing, oxygen levels, sleep quality, and daytime alertness.

What is CPAP therapy?

CPAP therapy requires a prescription from a doctor who specializes in sleep medicine. The doctor will conduct a sleep study to diagnose sleep apnea and determine the optimal pressure level for CPAP therapy. The pressure level may vary depending on the severity of sleep apnea, the type of mask used, and the sleeping position.

CPAP therapy consists of three main components:

  • CPAP machine: This is a small device that generates pressurized air. It has a humidifier that adds moisture to the air to prevent dryness and irritation. It also has a filter that removes dust and allergens from the air.
  • CPAP mask: This is a device that fits over the nose or mouth to deliver the pressurized air into the airway. There are different types of masks available, such as nasal masks, full-face masks, nasal pillows, etc. The mask should be comfortable and fit well to avoid leaks and ensure.
  • CPAP hose: The CPAP hose, also known as tubing, connects the CPAP machine to the CPAP mask, allowing the pressurized air to flow from the machine to the patient's airway. CPAP hoses come in various lengths and materials to accommodate different preferences and needs. 

How Lofta can help improve sleep with its CPAP solutions

Lofta offers comprehensive CPAP solutions designed to improve sleep quality and overall well-being. By partnering with Lofta, individuals seeking effective treatment for sleep apnea can access top-quality CPAP machines, masks, and accessories tailored to their specific needs. 

Lofta's CPAP solutions include the latest CPAP machines from leading brands, with built-in humidifiers and filters to ensure optimal air quality and comfort during therapy. Additionally, Lofta provides a wide selection of CPAP masks, including nasal masks, full-face masks, and nasal pillows, designed for maximum comfort and minimal leakage. Lofta also offers individuals who suspect they may be suffering from mild or moderate OSA the option to conduct an at-home sleep test, which is then reviewed by a health practitioner to determine the next steps, should the outcome be positive.

The expertise and personalized support provided by Lofta's team empower individuals to find the perfect CPAP setup for their unique preferences and sleep patterns. With Lofta's commitment to excellence and customer satisfaction, individuals can rest assured knowing they are receiving the best possible CPAP solution to improve their sleep and overall quality of life.

How Sleep Changes with Age

As we grow older, our sleep patterns change in various ways. Some of these changes are normal, while others may indicate underlying problems or disorders.


Children need more sleep than adults because they are growing and developing rapidly. They also spend more time in NREM sleep, which is important for growth hormone secretion, tissue repair, and immune function. Children also have more REM sleep than adults, which is essential for brain development, learning, and memory.

The average sleep duration for children varies depending on their age group. According to the National Sleep Foundation, the recommended sleep ranges are:

  • Newborns (0-3 months): 14 to 17 hours
  • Infants (4-11 months): 12 to 15 hours
  • Toddlers (1-2 years): 11 to 14 hours
  • Preschoolers (3-5 years): 10 to 13 hours
  • School-age children (6-13 years): 9 to 11 hours
  • Teenagers (14-17 years): 8 to 10 hours


Adolescence is a period of significant physical, emotional, and social changes that affect sleep patterns and needs. During puberty, the circadian rhythm shifts to a later phase, meaning that adolescents tend to feel sleepy later at night and wake up later in the morning. This is known as the "sleep phase delay" or the "eveningness preference".

However, this natural tendency often conflicts with early school start times, social obligations, and exposure to artificial light from electronic devices. As a result, many adolescents do not get enough sleep or have irregular sleep schedules, which can lead to daytime sleepiness, mood swings, poor academic performance, and an increased risk of health problems.

The average sleep duration for adolescents is about 8 to 10 hours per night, but many fall short of this recommendation. To improve their sleep quality and quantity, adolescents should:

  • Maintain a consistent bedtime and wake-up time, even on weekends
  • Avoid caffeine, nicotine, alcohol, and other stimulants in the evening
  • Limit the use of electronic devices before bed and keep them out of the bedroom
  • Create a comfortable and quiet sleeping environment
  • Avoid napping too long or too late in the day
  • Get regular physical activity and exposure to natural light during the day


Adults generally need about 7 to 9 hours of sleep per night, but this can vary depending on individual factors such as lifestyle, health conditions, and genetics. Some people may function well with less than 7 hours of sleep, while others may need more than 9 hours of sleep.

As we age, our sleep architecture changes in several ways. We tend to spend less time in NREM sleep, especially N3 or deep sleep, which decreases gradually after the age of 30. We also tend to have more frequent awakenings during the night, which can fragment our sleep and reduce its quality. These changes may be related to hormonal changes, medical conditions, medication use, stress levels, or environmental factors.

To optimize our sleep quality and quantity as adults, we should:

  • Follow a regular sleep schedule that matches our circadian rhythm
  • Practice good sleep hygiene habits such as avoiding caffeine, alcohol, nicotine, and heavy meals in the evening
  • Engage in relaxing activities before bed such as reading, listening to music, or meditating
  • Avoid checking the clock or using electronic devices if you wake up during the night
  • Seek medical advice if you have symptoms of a sleep disorder such as snoring, gasping for air, restless legs syndrome, or insomnia

Senior Years

Older adults (65 years and older) still need about 7 to 8 hours of sleep per night, but they may face more challenges in achieving this goal. They may experience changes in their circadian rhythm that make them feel sleepy earlier in the evening and wake up earlier in the morning. They may also have more difficulty falling asleep or staying asleep due to physical discomforts, medical conditions, medication side effects, or psychological issues.

  • Changes in sleep duration: Older adults may experience shifts in their sleep duration, often characterized by shorter overall sleep time and more fragmented sleep patterns.
  • Alterations in circadian rhythm: Aging can disrupt the body's internal clock, leading to changes in the timing of sleep-wake cycles. This may result in earlier bedtimes and awakenings, commonly referred to as advanced sleep phase syndrome.
  • Increased susceptibility to sleep disorders: Older adults are at higher risk of developing sleep disorders such as insomnia, sleep apnea, and restless legs syndrome, which can further exacerbate sleep disturbances and impair overall sleep quality.
  • Decreased sleep efficiency: Aging is associated with decreased efficiency in consolidating and maintaining sleep, leading to more time spent awake during the night and difficulties falling back asleep after awakenings.
  • Changes in sleep architecture: Beyond reduced deep sleep and increased night awakenings, older adults may also experience alterations in the distribution of sleep stages, including decreased REM sleep and more frequent transitions between sleep stages. These changes can impact cognitive function, memory consolidation, and emotional regulation.

Why Healthy Sleep Cycles Matter

Understanding the intricacies of sleep phases and stages is essential for optimizing our sleep quality and overall well-being. From the foundational roles of NREM sleep in physical restoration to the vivid dreaming of REM sleep crucial for emotional regulation and cognitive function, each stage contributes uniquely to our nightly rest. Moreover, recognizing the challenges that can disrupt our sleep, such as sleep apnea, underscores the importance of proper therapy in addressing these issues and restoring healthy sleep patterns.


What are the main types of sleep and how do they differ?

Sleep consists of two main types: non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. NREM sleep is further divided into three stages, while REM sleep is characterized by vivid dreaming and rapid eye movements.

How long does a typical sleep cycle last, and how many cycles do we experience per night?

A typical sleep cycle lasts about 90 minutes and repeats four to six times per night. Each cycle consists of alternating stages of NREM and REM sleep.

What are the functions of NREM sleep, particularly its three stages?

NREM sleep plays a crucial role in physical recovery, immune function, memory consolidation, and emotional regulation. Stage 1 helps transition from wakefulness to deeper sleep, Stage 2 promotes stability in arousal levels, and Stage 3 is the deepest and most restorative stage of sleep.

What distinguishes REM sleep from NREM sleep?

REM sleep is characterized by fast brain wave activity similar to wakefulness, muscle paralysis except for breathing and eye movements, rapid eye movements, and vivid dreaming. In contrast, NREM sleep is characterized by slow brain wave activity, muscle relaxation, and the absence of rapid eye movements.

How do sleep patterns change with age, particularly in older adults?

Older adults may experience reduced deep sleep, increased night awakenings, alterations in circadian rhythm, heightened susceptibility to sleep disorders, decreased sleep efficiency, and changes in sleep architecture. These changes can impact overall sleep quality and may require adjustments in sleep habits and therapy approaches.

What is the benefit of a White Noise Machine?

    A White Noise Machine can provide a consistent background sound that masks disruptive noises and creates a soothing environment for sleep. It helps drown out sudden noises or disturbances, such as traffic outside or household sounds, which can disrupt sleep and prevent individuals from falling asleep or staying asleep. The steady sound produced by a White Noise Machine can help promote relaxation, improve sleep quality, and enhance overall sleep experience by creating a more conducive environment for restful sleep.

    How does Specialty Bedding contribute to healthy sleep?

      Specialty Bedding, such as memory foam mattresses, adjustable beds, and temperature-regulating bedding, can contribute to healthy sleep by providing optimal support, comfort, and temperature control. Memory foam mattresses contour to the body's shape, relieving pressure points and promoting proper spinal alignment, which can reduce discomfort and improve sleep quality. Adjustable beds allow users to customize their sleep position for maximum comfort and alleviation of sleep-related issues, such as snoring or acid reflux. Temperature-regulating bedding, such as moisture-wicking sheets or cooling mattress pads, helps maintain a comfortable sleep temperature, preventing overheating or excessive sweating that can disrupt sleep. Overall, specialty bedding enhances sleep comfort and support, leading to better sleep quality and overall well-being.

      How do Health Monitors work?

        Health Monitors typically utilize sensors and technology to track various physiological parameters, such as heart rate, respiratory rate, sleep patterns, and physical activity levels. These monitors may come in the form of wearable devices, such as fitness trackers or smartwatches, or bedside devices that track sleep metrics. Wearable health monitors use built-in sensors to continuously monitor vital signs and movement throughout the day and night. They collect data, such as heart rate variability or sleep stages, and transmit it to a companion app or platform for analysis. Bedside health monitors may use similar technology to track sleep metrics, such as sleep duration, sleep efficiency, and sleep stages, by monitoring movement and breathing patterns. By providing insights into sleep quality, physical activity, and overall health parameters, health monitors empower individuals to make informed decisions about their lifestyle, habits, and healthcare needs, ultimately promoting better sleep and overall well-being.

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