Sleep Cycles Explained

Over a lifetime a person spends about 25 years of there life sleeping. That seems like allot doesn’t it? For example, lets say a person was 50 years old and they slept an average of 8 hours per day. That would mean they slept 146,000 hours. That would be about 6,083 days and about 17 years. That is just an estimation. Back in the 1950’s Universities started setting up sleep laboratories where people’s brain waves, respiration rate, eye movements, and more were monitored while they were sleeping. From those recordings researchers discovered two major things of sleep. There are two categories of sleep, the NREM and the REM.

NREM stands for Non Rapid Eye Movement and REM stands for Rapid Eye Movement. NREM is often called “quiet sleep” because there is no rapid eye movement and this is because the heart rate and the respirations are slow and regular. During this time the body has little movement and the brain activity and blood pressure are at their lowest points in the 24 hour period. NREM sleep has four different stages, stages 1-4. Stage 1 is the lightest sleep and stage 4 is the deepest sleep.

The majority of us envision sleep as a time of deep relaxation and calmness. But REM is anything but calm. REM is sometimes called “active sleep”. The brain activity is intense while in the REM sleep. The large muscles of your body like your arms and legs become paralyzed when you are in the REM sleep. Some researchers have said that this is to keep people from acting out there dreams. But there is a rare disorder in which people are not paralyzed during REM sleep. While dreaming they may become violent, which may cause damage to themselves, there bed partner, or there home. If you watch a sleeper while they are in REM you can see there eyes moving around under there eyelids.

It is during REM that vivid dreams occur. Eighty percent of people awakened from REM sleep will report having a dream. If a person is awaken for several minutes during REM sleep it will take them at least 30 minutes to go back to REM sleep. That is the reason some people are awaken during a dream and try really hard to go back to sleep quickly in hopes to continue the dream.

It may surprise you to know that sleep follows a fairly predictable pattern every night. Everyone sleeps in cycles. Each sleep cycle last about 90 minutes. You have one or more stages of NREM sleep and then a period of REM sleep. A typical night of sleep for a young adult begins with a few minutes of sleep in stage 1, sometimes called “light sleep”. Then the sleeper will descend into stage 2 sleep. In this stage they are in a little more deeper sleep and are harder to awaken. About half of a total nights sleep is spent in stage 2 sleep. The brain activity and more delta waves (slow waves) appear in the EEG as sleep slowly becomes deeper. Sleepers enter stage 3 when the EEg enters 20% delta waves. Stage 3 sleep is the beginning of slow wave sleep (or deep sleep). The delta waves continue to increase and when they reach about 50% you enter stage 4 sleep. Stage 4 is the deepest sleep and you are at the hardest point to be awaken.

So as you can see from my research the brain is very busy at night when you’re asleep. Sleep is the mysterious 1/3 of your life. In this research you have learned about the two categories of sleep, which are NREM and REM. You have also learned about the different cycles (stages) during sleep.