Stages of Non-REM Sleep



3 stages of Non-REM sleep.

 

As sleep progresses through a series s of four to five  sleep cycles throughout the night, the time spent in the REM stage gets longer and the time spent in Deep or Stage 3 sleep gets shorter

 

Stage 1

This is when we start getting drowsy and begin to transition from being awake to falling asleep. This is a relatively light form of sleep that for most of us lasts about 5 to 10 minutes. During this stage our heart, breathing rate, brain wave and eye movement begins to slow and muscles relax and Body temperature decreases. We can be easily awakened and may feel like we’ve not been to sleep. This is when my wife normally hits me and says I’m snoring to which I will get defensive and say “how can I be snoring when I’m not even asleep yet”. I’m sure I’m not the only person this happens to!

 

Some people also experience  jerky movements or sleep starts during this stage  which may wake the sleeper up, or  at least the person next to them! (Again, I suffer this affliction, much to my wife’s annoyance). Most of us only spend about 5 percent of our total sleep time in Stage 1 sleep.

 

Stage 2

Most of us then transition into Stage 2 sleep which typically lasts 10 to 25 minutes which is also considered a period of light sleep. During this stage, eye movement stops, heart rate slows, brain waves become slower and muscles relax even further. 

As the 4-5 x 90min sleep cycles throughout the night, we spend more time in stage 2 sleep than in any other sleep stage, accounting for about 55 percent of our total sleep time

 

Stage 3

Next we hit stage 3 sleep, which is often referred to as "slow wave," "delta wave" or "deep" sleep.

Stage 3 sleep is vital for us to feel refreshed for the next day. We typically spend more time in Stage 3 sleep during the first half of sleep than the second half.

 

Typically lasting 20 to 40 minutes, Stage 3 sleep is when our brain becomes less responsive we are most difficult to wake up – e.g.  “Sleep like the dead”. If we are woken from Stage 3 sleep we are generally quite disoriented and vague. Hence why we normally recommend naps shorter than 40mins to avoid drifting into Stage 3 sleep. 

 

During Stage 3 sleep our heart rate, blood pressure, breathing rate and temperature drop to their lowest levels and the body repairs and regenerates tissues, builds bone and muscle, and appears to strengthen the immune system.

This is also the stage when we are most likely to sleepwalk and talking  and experience nightmares/terrors

 

We tend to spend spend about 15% of our total sleep time in stage 3 sleep.

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