Optimal Sleep Cycle: The Science of Better Sleep


Do you feel tired during the day? Are you getting enough quality sleep at night? Getting enough quality sleep requires that you achieve an optimal sleep cycle at night.

Sleep was once thought to be state of inaction in which your brain and body would shut down to rest and recuperate from the day’s activities. After the invention of a device in the late 1920s that enabled scientists to measure brain activity during sleep, researchers found that sleep is actually dynamic and consists of multiple sleep cycles.

In this article, I will cover what a sleep cycle is, what is an optimal sleep cycle, the importance of an optimal sleep cycle, and the symptoms of an off-balance sleep cycle.

A Sleep Cycle

We need sleep to restore our bodies and minds and to maintain proper health. If you are a healthy adult with a normal sleep pattern, you should experience five stages of a cycle that each last about 90 minutes when you sleep: stages 1, 2, 3, 4, and REM or rapid eye movement. As you sleep, you should pass through each stage starting from stage 1 and ending in REM sleep before the cycle begins again with stage 1. The first four stages consist of non-rapid eye movement (NREM) sleep, and your sleep becomes deeper as you progress from stage 1 to stage 4. The following details each stage of the sleep cycle.

Stage 1 – In this step, you are in light sleep, shifting in and out of sleep, and something or someone can easily wake you up. Your body motion slows down, and eyes move very slowly. If you become awake during this stage, you may recall fragmented pictures in your mind.

Stage 2 – As you begin this stage, your eyes stop moving, and brain activity slows down. Sleep spindles or bursts of rapid brain waves may occur occasionally.

Stage 3 – Delta waves or very slow brain waves intermixed with smaller, more rapid waves develop during this step.

Stage 4 – By the time you are at this stage, your brain creates predominantly delta waves. When you are in stages 3 and 4, you are considered to be in deep sleep, and your eyes and body do not move. Waking you up in these stages is usually very difficult. Most people aroused while in deep sleep feel disoriented and confused for a short time after waking up.

REM sleep – Upon entering REM sleep, you breath more quickly, shallowly, and unevenly. Your eyes dart quickly in different directions, and your arms and legs become temporarily immobile. Your heart rate and blood pressure increase and you are more likely to dream in this stage.

Optimal Sleep Cycle

An optimal or most favorable sleep cycle in a healthy adult usually starts with NREM sleep. When you lay down on your bed to sleep, moving from being awake to stage 1 usually happens within minutes as your eyes start to move slowly.

Stage 1 of NREM sleep should ideally last between one to seven minutes.

Stage 2 comes next and lasts from 10 to 25 minutes. It is characterized by the occurrence of sleep spindles. As you Move into stage 3 of NREM sleep, your brain starts to create delta or slow waves, and you move into what is considered deep sleep.  This phase should ideally last between 20 and 40 minutes.

In stage 4, your brain moves into lighter NREM sleep for 5 to 10 minutes just before entering REM sleep. Once you are in REM sleep, your eyes begin to move in different directions, and you should stay in REM sleep between 10 and 20 minutes. The average length of a sleep cycle is about 90 minutes.

A typical night of sleep for most people, however, does not consist of putting a series of 4 to 6 sleep cycles. In reality, the time you spend in a certain stage changes during the night. In the first 2 to 3 cycles of a typical night of sleep, you are mostly in stages 3 and 4 of NREM sleep. In the last 2 to 3 cycles, you are mostly in REM sleep, occasionally drifting into NREM sleep. Most people, therefore, tend to be in NREM sleep during the early part of the night and REM sleep in the later part.

Optimal Sleep Cycle Importance

The reason for the complexity of sleep cycles remains a mystery, but one thing remains clear: all of us need to get enough NREM and REM sleep every night to feel rested and refreshed. In reality, there is no single optimal sleep cycle that applies to everyone, because the amount and types of sleep change depending on your age.

For example, most adults average about 8 hours of sleep per night, while teenagers average about 9 or more hours per night. However, teens typically spend 40% more time in NREM deep sleep (stage 3 and 4) than adults.

While there is no optimal sleep schedule that applies to everyone, getting enough of quality sleep is important.

Symptoms of Off-Balance Sleep Cycle

Sleep is a time for your body to heal and prepare itself for the next day’s activities. Not getting enough quality sleep will affect your ability to learn, work, and communicate at peak efficiency. Although requirements for sleep differ, most adults need about 7.5 to 9 hours of nightly sleep, teenagers 8.5 to 10 hours, and newborns 10 to 18 hours. The following are symptoms of being sleep deprived or having a sleep cycle that is not in balance (e.g., napping too much during the day).

  • Being moody and easily irritated
  • Problems with concentrating and remembering facts
  • Feeling exhausted and not motivated
  • Having difficulty coping with stress
  • Experiencing reduced ability to learn, create, and solve problems
  • Getting sick more often
  • Gaining weight


When you sleep at night, your brain and body undergo much activity and changes to prepare for the next day. Without sufficient and quality restorative sleep, you lack the energy and motivation to live and perform at your best. Knowing that we sleep in cycles that alternate between NREM and REM sleep means that we need to sleep long enough so that our bodies get enough NREM and REM sleep.

Has your daily routine ever been affected by an off-balance sleep cycle?  What did you do to bring it back to balance? Let us know in the comments.


1. http://healthysleep.med.harvard.edu/healthy/science/what/sleep-patterns-rem-nrem

2. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Understanding-Sleep

3. https://www.helpguide.org/articles/sleep/sleep-needs-get-the-sleep-you-need.htm

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