It’s 2 am, and you’re tossing and turning, mind racing with unfinished to-do lists. Eventually, you drift off, only to wake up groggy despite a seemingly full night’s rest. Sound familiar? Most of us take sleep for granted, assuming it’s just “lights out.” But behind the scenes, your body is hard at work, navigating a four-stage journey that restores you overnight.
From initial drowsiness to deep slumber, each stage of the sleep cycle serves a specific purpose in maintaining our overall wellbeing. In fact, various sleep conditions can easily disrupt our nighttime patterns, causing disturbances in individual phases or even the entire cycle.
Through a greater understanding of the science behind sleep – and how sleep problems can influence our restorative rest – we can unravel the mystery of our own sleep quality.
Learn more: Medical Channel Asia Sleep Page
What Goes On When You Sleep
When you hit the hay, your mind and body don’t just go dormant – they cycle through a series of four stages that are essential for physical and mental health.
The sleep cycle can be categorised into two sections: rapid eye movement (REM) sleep, and non-REM sleep. Non-REM sleep is further divided into three stages, which occur before you hit the REM phase.
What’s interesting is that this sleep cycle only lasts between 90 to 120 minutes. Considering that adults require about seven to nine hours of shut-eye each night, you can experience this cycle roughly four to six times after falling asleep.
Let’s start by breaking it down to its core components.
Stage 1: Lightest Sleep
A brief phase lasting 1–5 minutes where the body begins to relax. You can wake easily.
Marking the start of your sleep journey, this initial stage sets the tone for your nightly rest and rejuvenation.
This is when your body goes into repose; your eye movements, respiration, heartbeat and brain waves start to slow down (and declines even further along the non-REM stages), although your muscles can twitch every now and then.
Only lasting between one to five minutes, you can be easily awoken, and may not even be aware that you are drifting off, sliding you further down the depths of your unconscious being.
Stage 2: Light Sleep
The longest phase, lasting 10–25 minutes. The whole body relaxes. Unique brainwaves in this stage aid memory and protect against disturbances.
Stage 2 accounts for up to half the portion of your sleep cycle, and takes 10 to 25 minutes to process through.
Here, your whole body falls deeper into relaxation. Your eye movements finally stop, while your body temperature dips.
In addition, your brain is introduced to two unique brainwave patterns: sleep spindles and K-complexes.
Sleep spindles are sharp bursts of activity that are thought to facilitate a myriad of sleep-related operations, including memory consolidation and cognitive functioning. As for K-complexes, they act as a protective mechanism, preventing arousal and keeping you undisturbed from external stimuli if your brain has analysed it to be harmless.
Stage 3: Deep Sleep
Essential for tissue repair and immune health, this phase restores physical energy. It lasts 20-40 minutes early in the night and shortens as the night progresses.
As the last stage of non-REM sleep, your body enters a deep state of relaxation, with brainwaves slowing down significantly. At this time, your body takes the opportunity to maintain physical wellness by repairing tissues and bolstering the immune system.
This stage is crucial for feeling well-rested; if you have insufficient deep sleep, you can get up the next morning tired even after sleeping a full night.
Waking during this stage poses a challenge, leaving you groggy and disoriented for up to an hour. This stage lasts 20 to 40 minutes, although this does decrease in the later part of the night.
Stage 4: REM
Dreams occur as brain activity spikes. This phase is marked by rapid eye movement and temporary muscle paralysis, growing longer with each cycle.
This is the most exciting part of the cycle, holding a stage all on its own. Your heart rate, breathing, and brain activity quicken, resembling your awakened state during REM sleep.
Characterised by how your eyes roll swiftly beneath your lids, this phase is most associated with dreaming. To prevent your body from enacting your dreams, muscle atonia, or temporary physical paralysis, is triggered.
This phase initially lasts about 10 minutes but often stretches to 30 to 60 minutes later in the night.
Modern life, with the honking cars and phone alerts, can disrupt the delicate balance of your sleep cycle. Beyond that, the most hazardous disturbance to restorative rest are existing sleep conditions.
The Oppressiveness of Sleep Disorders
Sleep conditions can affect any part of the cycle. Let’s understand this further through the illustration of a few well-known disorders: restless leg syndrome (RLS) and narcolepsy.
Restless Leg Syndrome
Movement disorders like RLS are normally associated with the start of the sleep cycle, delaying your entry into the initial stages. Even worse, it can be paired with an issue that is all too relatable for many: insomnia.
“People with restless leg syndrome often suffer from insomnia because they are kept awake by this sensation of pulling or crawling itch.” explained Dr Prakash Kumar, a Senior Consultant in the Department of Neurology at National Neuroscience Institute, in HealthXchange.
“Unlike normal leg cramps which can be relieved by resting, RLS requires you to move or walk to get symptom relief.”
This struggle to transition smoothly into deeper sleep can hence lead to fragmented sleep patterns.
Narcolepsy
Narcolepsy is a neurological affliction that disrupts the sleep cycle in a unique way – people with this condition can almost surpass the non-REM phases to enter REM sleep very quickly, often within minutes of falling asleep.
The ease at which they fall asleep means they can experience dream-like hallucinations and the muscle weakness of sleep paralysis even during waking hours, and they often doze off during the day.
Sleep Deserves Your Attention
Think about the last time you woke up feeling unstoppable, like you could take on the world. That’s the power of good sleep! Each part of your sleep cycle play an important role in giving your body and mind the fuel they need to thrive.
Your sleep cycle is more than just a biological routine – it’s the foundation for how you feel, think, and function every day. If you are experiencing excessive daytime fatigue, it’s a sign to consult a doctor, and incorporate sleep hygiene practices to preserve your sleep cycles and guarantee better quality rest.
Sweet dreams!
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