Understanding our sleep cycle: REM and non-REM sleep

By Dr. Joti Samra, CEO & Founder of the Psychological Health & Safety (PH&S) Clinic and MyWorkplaceHealth

​Sleep is a core physiological function that impacts many other important areas of functioning (e.g., energy, mood, appetite, motivation, concentration, efficiency).  The average adult needs 6-9 hours of sleep. Consistently getting less than 6 hours per night leads to a range of health consequences, and consistently getting more than 9 hours leads to excessive lethargy and fatigue. Unfortunately, many of us struggle with mild to chronic sleep difficulties that impact our daily lives. Understanding our sleep cycle gives us insight into how our sleep patterns work and can help us identify the reasons why our sleep may be disturbed. 

Types of Sleep

We have 2 main types of sleep: non-REM and REM sleep. 

1. non-REM sleep is characterized by 3 stages of sleep that progressively deepen from light sleep, to restful sleep, to deep sleep. 
2. REM (rapid eye movement) sleep is characterized by dreaming and is the state in which restoration of our brain and body functions occurs, including energy conservation and memory consolidation.

Sleep Cycles 

We cycle through Stages 1, 2, 3, and REM throughout the night. Each cycle takes approximately 90 minutes and repeats. Also, as the night progresses we increasingly spend a longer period of time in REM (which leads to sleeping becoming more “restorative”, or restful the longer we sleep).  So, let’s talk about each stage individually. 

Stage One - we’re in transition between being awake and asleep. This is a state of very light sleep, and when we are awakened in stage 1 we may claim or feel we weren’t sleeping. 

Stage Two - is a light stage of sleep. It’s characterized by the slowing down of brain waves. 

Stage Three - is a stage of deep sleep – when we are woken from this stage, we’re often confused and disoriented. This is the stage during which bedwetting, sleepwalking or night terrors are experienced.

Stage Four or REM stage is the last stage in the cycle. In this stage, the eyes usually move fast in different directions and breathing patterns become irregular. Our limbs may also become paralyzed though the feeling is temporary. People who are awoken from this stage may have bizarre tales or wild dreams.

Once we leave REM sleep we start the cycle over again. 

Changes in our Sleep Cycle Sleep patterns are impacted by a range of factors, including stress levels, low mood and depression, worry, physical health conditions, medications, and worry about sleep.

Alcohol and many prescription drugs can help facilitate Stage 1 and 2 of sleep, but often have detrimental impacts on our more restorative Stage 3 and REM sleep.