Cycles of Sleep- The Stages of Sleep Explained

There are two different types of sleep. The first is non-Rapid Eye Movement sleep or non-REM sleep and the second is Rapid Eye Movement sleep known as REM sleep.


            Non-REM Sleep.

Non-REM sleep has three stages: non-REM one, non-REM two and non-REM three. Stage one of non-REM sleep happens at sleep onset and is considered the lightest form of sleep. You often enter the stage without realizing it. You spend about 5% of your total sleep time in the stage. Stage 2 is a deeper stage of sleep and you spend about 45% of your total sleep time in this stage. Stage 3, also known as slow wave sleep is a deep stage of sleep. You spend about 25% of your total sleep time in the stage.

                REM Sleep.

The rest of your time is spent in REM sleep. REM sleep is characterized by rapid movement of the eyes in addition to muscle paralysis or inability to move your muscles and dreaming. It’s a common misconception that we rest our brains when we sleep. On the contrary, your brain is often more active in REM sleep than it is when you’re awake.

The stages of non-REM sleep and REM sleep alternate in a repetitive cycle throughout the night. Four to five cycles occur per night and one cycle lasts approximately 90 minutes. Non-REM sleep is predominant in the early part of the night and decreases in intensity and duration whereas REM sleep increases in intensity and duration toward the end of the sleep period.

Researchers have studied the different stages of sleep using polysomnoGRAPHY or PSG. PSG measures the physiological changes that occur during sleep. It measures electrical brain activity, eye movement muscle activity and heart rhythm.

Napping is an excellent strategy for improving alertness performance and health the best time to nap are when you’re experiencing a low point in your biological clock dependent alerting. As mentioned earlier this is around 3 to 5 p.m. in the afternoon. Naps lasting 20 to 45 minutes are ideal. Naps lasting longer than this can actually make you feel tired because you’re more likely to wake up out of a deeper sleep. Long naps will also interfere with nighttime sleep and can does reduce your ability to sleep through the night. So the trick is to keep naps short and to take a nap when you feel a dip in your alertness.

The biology of sleep is complex, but the reason for why you need to sleep is simple. Sleep improves your memory promotes your health and prevents disease. It’s no wonder why it makes up one third of our lives. But what happens when sleep goes wrong?


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