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The sleep cycle consists of two main parts: REM and Non-REM, with intermediary stages. Understanding the stages of the sleep cycle can help you understand how to time your sleep, how to achieve memorable and even lucid dreams, and even to know what stage of sleep you were in when you are woken up unexpectedly.
Stage 1: The first stage of sleep is actually the drifting off between sleep and wakefulness. This stage may last several minutes, but usually not longer than 15 minutes. If you are awakened during Stage 1, you may feel like you haven’t even fallen asleep yet; in fact, you have. It is common for people with insomnia to stay in Stage 1 for a very long time, and every time they wake they feel like they haven’t slept yet, which causes frustration and makes it very difficult to relax and fall asleep into Stage 2.
Stage 2: This stage is characterized by very light sleep, slowly moving to deeper sleep. Your body will tense and relax intermittently and your breathing will become slow and deep as Stage 2 progresses. Your body temperature will also decrease during this stage, and if you are not properly covered with blankets or if your room is too cold, this is the point at which you might wake shivering.
Stage 3: This is the first stage of deep sleep, though not yet characterized by dreams. The brainwaves slow to the higher levels of Delta frequency, and your brain prepares to enter Stage 4 deep sleep.
Stage 4: This is the second level of deep sleep, the last level of non-REM sleep before dreams begin. At Stage 4, your brain is producing the lower levels of Delta frequency brainwaves. If you are awakened during Stage 4, you are likely to feel disoriented, perhaps not knowing where you are.
REM Sleep: This is the stage at which you dream. REM stands for “Rapid Eye Movement.” REM sleep is characterized by paralysis in your major voluntary muscle groups, but quick movement in your eyes, erratic breathing, and brain waves at faster levels than before, mimicking the brain wave patterns of waking consciousness. During dreams, your brain works through problems and questions that were posed to it during your waking hours, or visits unresolved issues that your conscious mind may not even be aware of. You may find that when you wake up from a good night’s sleep your mind is clear and things that were confusing and problematic the night before are clear and easy to understand. This is because of the brain activity during REM sleep. Your body may look like you are sleeping, but your brain is doing very important work.
After a certain amount of time in REM sleep, you will move back to Stage 1, possibly even waking for a short time in between. Most people do not remember these waking times, though they are very common. Early in the night, your periods of deep sleep are long while your REM period is short; late in the night and towards the morning, this switches so that you spend a short amount of time in deep sleep and a longer period of time in REM sleep. For most people, a sleep cycle takes about 90 minutes. Many experts recommend timing your sleep in 90-minute increments instead of in hourly increments so as to increase your chances of waking up refreshed between REM and Stage 1, rather than waking up disoriented during Stage 3 and 4 or REM.
If you are not getting enough sleep, you are likely to suffer from memory impairment or loss, difficulty concentrating, dozing off especially while driving, fatigue, immune system problems, or depression. Even if you are getting nine hours of sleep a night, if you suffer from these symptoms, the problem is likely your sleep: you are probably getting poor quality sleep. You may have a hard time moving from Stages 1 and 2 to deep sleep and REM. Sleep disorders such as sleep apnea can wake you many times during the night, even if you do not remember waking up, and have the effect of preventing you from sleeping soundly. Drinking caffeine too late at night can also negatively impact your sleep. This is a double-edged sword, however, as stimulants such as caffeine are often necessary for a sleep-deprived person to be able to work during the day.
Sleep deprivation is a major problem in the modern world, with artificial lights and computers extending the work day long into the hours of darkness. Current polls indicate that the vast majority of adults get less than seven hours of sleep a night, while sleep experts recommend that adults get a minimum of seven and a half hours of sleep, and up to nine hours. Children need far more sleep than this, and even up through high school they need up to 10 hours of sleep a night. Contrary to popular myths, sleep deprivation is not something your body can get used to. In fact, sleep deprivation compounds until you are dealing with chronic sleep deprivation, which is a problem all of its own.
Because REM sleep occurs last in the sleep cycle, and because the most REM sleep happens the latest at night and in the morning, if you find that you never remember your dreams, it is possible that you are not getting enough sleep to get into a good long REM cycle. Some tips for getting longer and better sleep include: avoiding stimulants for a few hours before bed, having a relaxing bedtime routine, darkening your room by covering up the alarm clock and putting blackout curtains in the windows, lowering the temperature of the room, and using a soothing fragrance such as lavender or eucalyptus.