Rest & Relaxation

Sleep Cycles

Lesson 3 Chapter 1

What Is A Sleep Cycle?

A sleep cycle is the progression through the various stages of Non-REM sleep to REM sleep before beginning the progression again with Non-REM sleep. Typically, you would begin a sleep cycle every 90-120 minutes resulting in four to five cycles per sleep time, or hours spent asleep.


Non REM Sleep

You do not go straight from deep sleep to REM sleep. Rather, a sleep cycle progress through the stages of non-REM sleep from light to deep sleep, then reverse back from deep sleep to light sleep, ending with time in REM sleep before starting over in light sleep again.


REM Sleep

REM can occur at any time during the sleep cycle, but on average it begins 90 minutes following sleep onset and is short in duration as it is the first REM period of the night. Following REM, the process resumes starting with periods of Stage 1, 2 & 3 intermixed before returning to REM again for longer periods of time as sleep time continues.

“The average cycle is 1 hour and 30 minutes, however cycle length can vary from 60-120 minutes depending on the person.”



Everyone dreams.  You spend about 2 hours each night dreaming, but may not remember most of your dreams.  Its exact purpose isn’t known, but dreaming may help you process your emotions.  Events from the day often invade your thoughts during sleep, and people suffering from stress or anxiety are more likely to have frightening dreams.  Dreams can be experienced in all stages of sleep but usually are most vivid in REM sleep.  Some people dream in colour, while others only recall dreams in black and white.


Effective Sleep Cycles

If you truly were to sleep without any disturbances and no alarm clocks, you would always wake up on a multiple of 90 minutes.

For example after: 4.5 hours, 6 hours, or 9 hours of sleep.

Non-REM sleep lasts about 70 minutes per cycle, while REM sleep lasts about 20 minutes per cycle.


“A person who only gets 4 cycles of undisturbed sleep (6 hours) will actually be much more rested than a person who has slept for 8-10 hours but who has not been allowed to complete any one cycle because of being awakened before it was completed.”


Want To Wake Up Easier? Don’t Wake Up In REM Sleep!

The time between REM sleep (stage 4) and Stage 2 is called the Twilight Zone (Stage 1). The Twilight Zone is the brief period inbetween each 90 min. sleep cycle. If you are in Stage 1 of sleep, it is very easy to wake up. You will find that any light stimulus will wake you, from a light noise to the sun rising.

Waking up in the second half of your sleep cycle (especially during REM sleep) is often very difficult. Many people report not being able to wake up.

When you are in REM sleep, your motor output system from the brain is completely shut down (this is why you dream that you are running but you don’t actually run) and also explains why you feel so lifeless when you wake up during REM sleep! Now of course, the motor output system doesn’t always turn off, and we see this especially with sleepwalkers.


When To Wake

However, if you wake up in the beginning stages of sleep (especially the Twilight Zone), you will find that you wake up easier and feel so refreshed when you get up. 

Keep a Journal to Help

Record the beginning and waking times for each natural sleep episode that is uninterrupted by an alarm or other disturbance. Find the common multiple. For example, if your recorded sleep periods were 400, 500, 400, 200, and 700 minutes, you would conclude that your personal sleep cycle typically lasts 100 minutes, or 1.6 hours. If you don’t want to keep a journal, just assume it is 90 minutes in length.

Tips To Help

  • Plan your waking accordingly:  For example, if your cycle is 90 minutes and you fall asleep at midnight every night, you should plan to wake at any of the following times: 6am, 7:30am, or 9am. All three of these times are multiples of 90 minutes. You would technically be waking up after a full sleep cycle, ideally. If you got up at 8:30am, you would be getting up in the later stages of sleep and would probably find it more difficult to wake up. 
  • Visualise Waking Up: In an interesting study published on Sleep in 1997, participants were asked to visualise their time of waking on an imaginary clock face. Results found that those who visualised what time they had to get up were naturally able to wake up at the desired time without any alarm. 


Each sleep cycle lasts for about 90 minutes. If you sleep for 8 hours a day that gives you time to go through a bit over 5 cycles a night. Multiply it by 7 (the number of days in a week) and you’ll have 35 cycles. 

The key techniques: Get the same amount of sleep nightly, visualise the time you want to wake up, and use a back up alarm.