Understanding how sleep works is the first step to improving it. At the core of quality sleep is something called a sleep cycle this is a dynamic series of stages your brain and body pass through multiple times each night. But how long is a sleep cycle, and why does it matter? In this guide, CPAP Discount Warehouse’ll explore the science behind sleep cycles, how they change across the lifespan, and how to use this knowledge to sleep smarter.
What Is a Sleep Cycle?
Sleep isn’t uniform. Throughout the night, you cycle through four stages of sleep. On a typical night, a person experiences four to six sleep cycles. While not all cycles are the same length, they typically last about 90 minutes each.
The first cycle is often the shortest, ranging from 70 to 100 minutes, while later cycles tend to last between 90 and 120 minutes. Additionally, the composition of each cycle, or how much time is spent in each phase of sleep, changes throughout the night.
4 Stages of Sleep Cycles
Even though you're sleeping, your brain isn't completely inactive. Although you’re less aware of your surroundings, your brain is still very active. This activity exhibits predictable patterns. Experts have organized these patterns into stages. These stages fall into two categories: rapid eye movement (REM) sleep and non-REM (NREM) sleep.
What Are the Stages of Non-REM Sleep?
There are three NREM stages
+ Stage 1 (N1) is the lightest stage of sleep and occurs as a person first falls asleep. It typically lasts a few minutes, making up about 5% of your sleep time. People in this stage can be awakened easily and may experience sudden muscle jerks or a sensation of falling.
+ Stage 2 (N2) is also light sleep, but it is deeper than Stage 1. During this stage, your brain waves slow down and noticeable pauses occur between short, powerful bursts of electrical activity. Stage 2 sleep accounts for about 45% of total sleep time. You will go through multiple rounds of stage two non-rapid eye movement (NREM) sleep, and each round will usually be longer than the previous one. After Stage 2, you either transition to Stage 3 NREM sleep or enter REM sleep.
+ Stage 3 (N3 or Deep Sleep) is the deepest stage of sleep. In adults, it accounts for about 25% of total sleep time. During this stage, brain waves slow down significantly. Your body takes advantage of this deep stage to repair injuries and strengthen your immune system.
You need stage 3 NREM sleep to wake up feeling rested. Without enough of it, you will feel tired and drained, even after sleeping for a long time. This is why your body tries to fit as much stage three sleep into your sleep period as early as possible.
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What Happens During REM Sleep?
Stage 4 REM Sleep (Rapid eye movement sleep) is the stage of sleep during which most dreams occur. During REM sleep, your eyes move rapidly from side to side behind your closed eyelids, and your brain activity resembles that of an awake person.
REM sleep accounts for about 25% of your sleep cycle. It first occurs 70–90 minutes after falling asleep. Each subsequent period is longer than the previous one, up to an hour.
How Long Is a Sleep Cycle?
Not all sleep cycles are the same length, but on average, each one lasts about 90 minutes. The first sleep cycle is often the shortest, lasting between 70 and 100 minutes, while subsequent cycles usually last between 90 and 120 minutes. However, this duration is not fixed and can range between 70 to 110 minutes, depending on:
+ Age: Newborns spend far more time in REM sleep and sometimes enter this stage as soon as they fall asleep. As they grow older, their sleep patterns become similar to those of adults. Older adults tend to spend less time in REM sleep.
+ Alcohol: Alcohol and some other drugs can alter sleep architecture
+ Sleep disorders: Conditions such as sleep apnea and restless legs syndrome (RLS), which cause frequent awakenings, can disrupt a healthy sleep cycle.
+ Circadian rhythm: Establish a sleep schedule and stick to it. Try to wake up and go to bed at the same time each day.
Sleep cycle length by age
Sleep cycle length by age is an important factor to consider when evaluating sleep quality or using a sleep calculator.
| Age | 20 | 40 | 60 | 70 | 80 |
| Time to fall asleep | 16 minutes | 17 minutes | 18 minutes | 18.5 minutes | 19 minutes |
| Total sleep time | 7.5 hours | 7 hours | 6.2 hours | 6 hours | 5.8 hours |
| Time in regular sleep | 47% | 51% | 53% | 55% | 57% |
| Time in slow wave sleep | 20% | 15% | 10% | 9% | 7.5% |
| Time in REM sleep | 22% | 21% | 20% | 19% | 17% |
| Time asleep while in bed | 95% | 88% | 84% | 82% | 79% |
How many sleep cycles per night?
Adults typically require 5 full sleep cycles, equating to 7.5–8 hours of sleep. However, how many sleep cycles per night you get depends on your schedule and sleep habits.
| Hours Slept | Approx. Cycles | Sleep Quality |
| 4.5 hours | 3 | Poor |
| 6 hours | 4 | Moderate |
| 7.5 hours | 5 | Ideal |
| 9 hours | 6 | Optimal (for some) |
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What Affects Sleep Stages?
Several biological and neurological factors can influence how the body transitions through the stages of sleep. These disruptions can affect sleep depth, duration, and the restorative value of each cycle, especially stages like deep sleep (N3) and REM. Here are five major contributors:
Depression
+ Individuals with depression may enter REM sleep earlier (shortened REM latency).
+ They often experience increased REM density, which may disrupt the balance of sleep stages.
+ Deep sleep (N3) may be reduced, leading to less restorative rest and more frequent awakenings.
Aging
+ Older adults typically experience lighter sleep, spending more time in stages N1 and N2.
+ Deep sleep (N3) tends to decrease significantly, often starting in middle age.
+ Nighttime awakenings become more frequent, and sleep efficiency may decline.
Traumatic Brain Injuries (TBI)
+ Damage to brain areas that manage circadian rhythm and sleep-wake cycles can lead to fragmented or abnormal stage transitions.
+ Individuals may experience increased light sleep, reduced deep sleep, or disruptions in REM onset.
+ Some may also develop hypersomnia or insomnia, depending on the location and severity of injury.
Medications
+ Antidepressants (especially SSRIs and TCAs): Often suppress REM sleep.
+ Benzodiazepines and sedatives: Increase N2 sleep but reduce deep sleep and REM.
+ Stimulants (e.g., ADHD medications): Delay sleep onset and reduce total sleep time.
+ Opioids: Can significantly reduce both deep sleep and REM.
Circadian Rhythm Disorders
+ Conditions like Delayed Sleep Phase Disorder or Shift Work Disorder can cause sleep to occur at biologically “wrong” times.
+ As a result, the natural progression through stages, especially REM and deep sleep that may be interrupted or diminished.
+ Circadian misalignment often leads to fragmented sleep, reduced sleep efficiency, and daytime fatigue.
FAQs
How Much Deep Sleep Is Normal?
Deep sleep is essential for health and well-being. Most adults need 1.5 to 2 hours of deep sleep per night. The Centers for Disease Control and Prevention (CDC) recommends that adults aged 18–60 aim for at least seven hours of sleep per night. About 25% of that should be deep sleep.
Which is better, REM or deep sleep?
Previously, it was believed that REM sleep was the most important phase of sleep for learning and memory. However, new data suggests that non-REM sleep is actually more important for these processes. Non-REM sleep is also the more restful and restorative phase.
What Is the REM Phase of Sleep?
During REM sleep, your eyes twitch and your brain is active. This brain activity resembles that which occurs during waking hours. Dreaming usually occurs during REM sleep. To prevent you from acting out your dreams, your muscles become limp.
Is 6 hours sleep a night enough?
While some people can function on short periods of sleep, research generally agrees that six hours is insufficient for most adults. Experts recommend that adults get at least seven hours of sleep each night.
Understanding the science behind our sleep equips us to value it more. A good night's sleep goes a long way in maintaining a healthy lifestyle, enhancing cognitive functions, and uplifting mood. By prioritizing sleep, we can optimize our daily productivity and foster overall well-being. So, here's to embracing the journey of sleep, a truly restorative and rejuvenating adventure for our bodies and minds. Sleep well, dream better, and wake up to a healthier you!
Sleep is an incredible part of our lives, deeply woven into the fabric of our health. So, here's to understanding it better, embracing its power, and making every night a rejuvenating journey towards a healthier day. Remember, sleep well, dream better, and wake up to a healthier you with cpapdiscount.au
