The Stages and Cycles of Sleep
The human body requires regular sleep to maintain proper function and health. In fact, we are biologically programmed to sleep every night to allow adequate restoration time for our mind and body. To understand sleep, we need to understand how the brain separates it into stages, and what the stages of sleep mean.
There are four stages of sleep: the first three stages fall under non-REM (NREM) sleep and the fourth is REM (rapid eye movement) sleep.
NREM Sleep, Stage 1 is the shift from wakefulness to sleep. This is the lightest stage of sleep and is often defined by slow eye movement and a shift in brainwave activity. This drowsy sleep stage can be easily disrupted, causing awakenings or arousals, and it’s also when people may experience hypnic jerks, an involuntary muscle spasm that occurs as a person is drifting off to sleep, or even the sensation of falling while drifting in and out of Stage 1.
In NREM Sleep, Stage 2, slow moving eye rolls cease, body temperature begins to decrease, heart rate begins to slow, and sudden awakenings don’t occur as easily as in Stage 1. Brainwave activity slows but is marked by brief bursts of electrical activity. You spend more of your repeated sleep cycles in Stage 2 sleep than in other sleep stages.
Stage 3 is known as deep NREM and is the most restorative stage of sleep and occurs in longer periods during the first half of the night. Awakenings or arousals are rare and often it is difficult to awaken someone in Stage 3 sleep. Parasomnias, abnormalities or undesirable behaviors that occur during transitions between sleep stages like sleepwalking, sleep talking, and night terrors, occur during the deepest stage of sleep.
REM sleep, Stage 4, is named for the fact that your eyes move rapidly from side to side behind closed eyelids, which first occurs about 90 minutes after falling asleep and is commonly known as the dreaming stage. Your brainwave activity, breathing, heart rate, and blood pressure becomes more like that seen in wakefulness. As you age, you sleep less of your time in REM sleep. Memory consolidation most likely requires both non-REM and REM sleep.
Our progression through these stages of sleep is called a sleep cycle. A single sleep cycle goes through the various stages of NREM sleep to REM sleep before starting over again with NREM sleep. Typically, a person would begin a sleep cycle every 90-120 minutes, resulting in four to five cycles per sleep time.
REM can occur at any time during the sleep cycle, but on average it begins 90 minutes following sleep onset and is short in duration as it is the first REM period of the night. Following REM, the process resumes, starting with periods of Stages 1, 2 & 3 intermixed before returning to REM again for longer periods of time as sleep time continues.
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To see if you’re getting your best night’s sleep just fill out our sleep questionnaire and come talk to a Factory Mattress sleep expert today!