Sleep consists of two main phases: REM (Rapid Eye Movement) sleep and NREM (Non-Rapid Eye Movement) sleep, sometimes referred to as sleep stages. Understanding these cycles can help us better comprehend how our bodies recover during the night.
Few people realize that while sleeping, we experience moments of rapid eye movement and even brief awakenings that we don’t consciously perceive. But what exactly are the different sleep stages, and what happens during each of them?
Sleep occurs in cycles, and each cycle includes different stages that serve essential functions for the body and brain. While sleep is vital for life, many people underestimate its importance, often shortening their sleep due to work obligations. This negatively affects overall health, leading to exhaustion and a weakened immune system, making us more susceptible to infections.
Adults should get at least 8 hours of sleep per night to allow the body to regenerate. During this time, we go through multiple sleep cycles, each playing a crucial role in rest and recovery.
The Four Sleep Stages and Their Impact on Sleep Quality
A full sleep cycle lasts approximately 90–110 minutes, with each stage lasting between 5–15 minutes. The quality of our sleep depends on how well we transition through these stages.
Stage 1: NREM – Falling Asleep
This first stage is the transition from wakefulness to sleep, lasting about 15 minutes. During this phase, our brain waves shift from beta waves (wakefulness) to alpha waves (relaxation).
What happens during this stage?
- Slow eye movements begin.
- Muscle tone decreases.
- Occasional muscle twitches or sudden jerks may occur.
- Some people experience a "falling" sensation.
- Light sleep allows for easy awakening.
Stage 2: NREM – Light Sleep
During this second stage, the brain waves slow down even further.
- The body fully relaxes.
- Body temperature decreases.
- Heart rate slows.
- Conscious awareness of surroundings disappears.
If someone wakes up abruptly in this stage, they may experience headaches due to the body's transition to deep sleep.
Stage 3: NREM – Deep Sleep
The third stage is where the body enters deep sleep, marked by slow, long brain waves.
What happens during this stage?
- The body undergoes physical recovery.
- Muscles fully relax, but muscle tone remains low.
- The brain enters slow-wave sleep (SWS).
This is considered the deepest stage of sleep, making it difficult to wake someone up. If a person is awakened during this stage, they may feel disoriented, confused, and fatigued.
This is also the stage where sleepwalking (somnambulism) and night terrors may occur.
Stage 4: REM Sleep – Dreaming Phase
The fourth stage is REM sleep, also called the "rapid eye movement" phase.
What happens during REM sleep?
- Breathing becomes irregular.
- Eye movements increase.
- Brain activity spikes.
- Heart rate increases.
- Body temperature rises.
- Muscles become completely paralyzed (to prevent movement while dreaming).
This is when dreaming occurs. The brain actively processes memories and stores new information from the previous day. The first REM phase occurs about 90 minutes after falling asleep.
Sleep Cycle Individuality
Not everyone experiences sleep in the same way. Factors like genetics and age influence sleep duration and quality.
For some individuals, a full sleep cycle lasts only 80 minutes instead of the usual 90–110 minutes. This means they need less sleep compared to those with longer sleep cycles.
How Much Deep Sleep Do We Need?
There is no universal answer to this question, as sleep needs are highly individual. Some people can fully recover with just 6 hours of sleep, while others require 8 hours or more.
Every phase plays a critical role in our well-being. Without the initial falling-asleep phase, we wouldn’t transition into deep sleep, which is necessary for body repair and memory consolidation.
With age, sleep needs change.
- Newborns and infants sleep the longest.
- Children and teenagers gradually need less sleep.
- Older adults sleep the least.
An interesting fact: Throughout the night, sleep cycles repeat 4–6 times, and REM sleep phases become longer as the night progresses.
The Importance of a Sleep Routine
Maintaining good sleep hygiene is essential for optimal rest. Many people struggle to find the answer to "How do I fix my sleep schedule?" Here are some key recommendations to improve sleep quality:
Tips for a Healthy Sleep Schedule
1. Maintain a Regular Sleep Schedule
Go to bed and wake up at the same time every day, even on weekends.
2. Reduce Light Exposure Before Bed
- Avoid screens (phones, tablets, and computers) at least 2 hours before sleep.
- Blue light from screens disrupts melatonin production and reduces sleep quality.
3. Get Fresh Air and Daylight
- Exposure to natural light during the day regulates your circadian rhythm.
- Outdoor physical activity, especially in the afternoon, promotes better sleep.
4. Avoid Stimulants Before Bed
- Limit caffeine, alcohol, and smoking before bedtime.
- These substances interfere with sleep quality and delay deep sleep phases.
5. Set the Right Room Temperature
- The optimal bedroom temperature is 18–22°C (64–72°F).
- A cool and well-ventilated room promotes deeper sleep.
6. Relax Before Sleep
- Reduce stress and stimulation at least 3 hours before bed.
- Try calming activities such as:
- Relaxing music
- Nature sounds
- Meditation
- Breathing exercises
- Aromatherapy (lavender, chamomile)
7. Be Mindful of Your Diet
- Avoid heavy meals before bed.
- Eating too close to bedtime forces digestion to work overnight, disrupting sleep quality.
- Recommended eating schedule: at least 2 hours before bed.
8. Invest in Sleep Comfort
- Choose the right mattress and bedding.
- A good weighted blanket can enhance relaxation.
9. Ensure Good Air Quality
- Ventilate your bedroom regularly for fresh air.
Final Thoughts on Sleep Hygiene
Each of us has control over our sleep habits and environment. Sleep hygiene includes daily habits, bedtime rituals, and environmental adjustments that optimize rest.
Even if you can’t follow all recommendations, try focusing on a few key changes—you’ll soon notice the benefits of high-quality sleep on your health and energy levels.
