Understanding Sleep Cycle Stages: Methods for Calculating Sleep Cycle Duration

Modern city dwellers lead busy lives and often neglect the importance of sleep, thus affecting their physical and mental health. To maintain good sleep quality, it's essential to understand the principles of the sleep cycle . The sleep cycle consists of different stages , each playing a different role in bodily repair and memory consolidation. Below, we introduce the different stages of the sleep cycle and how to calculate sleep cycle duration to help you plan your sleep time and improve overall sleep quality.

What is a sleep cycle ?

A sleep cycle refers to the complete process by which a person transitions from light sleep to deep sleep and finally to rapid eye movement (REM) sleep. Generally, a complete sleep cycle lasts about 90 minutes. This cycle repeats throughout the night, affecting the body's repair processes, memory consolidation, and mood regulation.

How many stages are there in a sleep cycle ?

When we fall asleep, our bodies go through multiple sleep cycles , each lasting about 90 minutes, and we typically experience 4 to 6 sleep cycles per night . These sleep cycles consist of 4 main stages , including 3 non-rapid eye movement (NREM) sleep stages and 1 rapid eye movement (REM) sleep stage. NREM sleep begins with light sleep and gradually progresses to deep sleep, while REM sleep is related to memory processing, learning, and dream formation. These stages cycle through the sleep cycles , influencing physical recovery and brain function.

Phase 1 (NREM 1)

This is the transition from wakefulness to sleep, lasting approximately 1 to 7 minutes. During this sleep cycle stage , brain activity begins to slow down, and heart rate, breathing, and muscle activity also become slower. This stage of sleep is very light, and it is easy to wake up if disturbed.

Phase 2 (NREM 2)

This is the main stage of sleep, accounting for about 40% to 50% of the total sleep time, and each episode lasts about 10 to 25 minutes. During this stage, body temperature drops, eye movements stop, and brain wave activity slows down, but brief and rapid brain wave activity occurs, which helps with memory organization and learning.

Phase 3 (NREM 3)

Deep sleep typically lasts 20 to 40 minutes. During this stage of the sleep cycle , the body is completely relaxed, muscle tension decreases, blood pressure drops, and the body begins to repair itself, helping to restore physical strength.

Phase 4 (REM)

This is the rapid eye movement (REM) sleep stage, which typically begins about 90 minutes after falling asleep and lasts 10 to 60 minutes each time. During this stage, brain activity is similar to that of the waking state, with rapid eye movements and irregular heart rate and breathing. Most dreams occur during this stage, and REM sleep also helps regulate mood and consolidate memories.

Is a sleep cycle always 90 minutes long?

While the average sleep cycle lasts about 90 minutes, the actual length can vary depending on individual constitution, age, and lifestyle. Some people may have sleep cycles as short as 70 minutes or as long as 110 minutes. Sleep quality does not depend on the length of a single cycle, but rather on whether multiple complete sleep cycles are experienced , allowing the body and brain to fully repair and rest.

Sleep cycle calculation and daily routine arrangement methods

Everyone's sleep duration varies depending on age, lifestyle, and physical condition. Calculating and planning your sleep schedule based on your natural sleep cycle can help avoid waking up during deep sleep, thus improving your mental state. You can start by calculating the average length of a complete sleep cycle (approximately 90 minutes) and then gradually adjust it to your optimal bedtime based on your individual needs.

Step 1: Decide on your wake-up time

For example, you need to get up at 7:00 AM. It is recommended to get up at the same time every day to allow your body to gradually adapt, which helps improve overall sleep quality and makes it easier to fall asleep at night.

Step 2: Calculate sleep cycles

Since the ideal sleep duration typically consists of 4 to 6 complete sleep cycles , and based on the average length of a complete sleep cycle (approximately 90 minutes), the optimal time to fall asleep is as follows:

• 4 sleep cycles (approximately 6 hours): Falling asleep at 1:00 AM

• 5 sleep cycles (approximately 7.5 hours): Fall asleep by 11:30 PM

• 6 sleep cycles (approximately 9 hours): Fall asleep at 10:00 PM

Step 3: Allow sufficient time for falling asleep

It usually takes 10 to 20 minutes for most people to fall asleep, so it is recommended to go to bed 15 minutes earlier to allow your body to relax and fall asleep.

Assessment and Adjustment

Since everyone's sleep cycle length and sleep needs are different, in addition to calculating sleep cycles , you can also use the following questions to assess whether you are getting enough sleep and make adjustments accordingly:

• Do you feel refreshed and energized when you wake up?

• Do you often feel tired during the day?

• Do I need coffee or tea to stay awake?

• Do you toss and turn, move around, or even snore while sleeping?

If you find yourself still feeling tired when you wake up, you may need to make further adjustments to your sleep schedule or lifestyle, such as adjusting your bedtime and wake-up time, avoiding caffeine before bed, and improving your sleep through supplements.

Further Reading: Poor Sleep Quality Has Significant Impacts! Products That Can Increase Deep Sleep and Improve Sleep Quality

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The above information explains how to calculate sleep cycle stages and duration , helping you plan your sleep schedule and improve your overall mental state. If you have any questions about NeoYouth's NMN15000+12000Ex Five-Fold Anti-Aging Formula , please contact us for product information.

References:

How Sleep Works - Sleep Phases and Stages | NHLBI, NIH

Sleep: What It Is, Why It's Important, Stages, REM & NREM 

The Science of Sleep: Understanding What Happens When You Sleep | Johns Hopkins Medicine

Sleep Calculator: How Much Sleep Do You Need?