Sleep cycle

Our brain goes through sleep cycles five or six times during the night. One sleep cycle consists of 5 stages and the whole period of 5 stages takes about 90 minutes.

There are four stages of sleep: Non-REM (NREM) sleep (Stages 1, 2 & 3) and REM sleep. Periods of wakefulness occur before and throughout the various sleep stages or as one shift sleeping position.

Stages of sleep
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Stages of sleep

Stage 1

This first stage of sleep cycle is the lightest stage of NREM sleep and it lasts about 5 minutes, your eyes are slowly moving under the eyelids, and you are quickly awakened. Occasionally people may experience abrupt muscle spasms and may even experience a sensation of falling during the Stage 1 .

Stage 2

This is the first actual stage of defined NREM sleep.  Awakenings or arousals do not occur as easily as in Stage 1 sleep and the slow-moving eye rolls discontinue. Body temperature begins to decrease and heart rate begins to slow.

Stage 3

Stage 3 is known as deep NREM sleep. You are difficult to be awakened at this stage, and if it happens, you cannot adjust immediately to the reality. This is the most profound stage of your sleep, at this time, blood flow directed to your muscles to restore the physical energy.  The brain waves at this time are languid, these waves referred to as delta waves. Sleepwalking, sleep talking and night terrors occur during the deepest stage of sleep

Stage 4 or REM Sleep 

REM sleep – also known as rapid eye movement, is the most commonly known dreaming stage. You enter this stage after about 70-80 minutes after falling asleep. This is the time when you see dreams, your eyes are frequently moving, your breathing shallow and your heart rate increases. Also, at this time your arm and leg muscles are paralyzed.

Stage 3 and 4 are particularly important for the body. The most damaging effects of sleep deprivation are from the inadequate deep sleep.  It is the time when the body repairs itself and builds up energy for the next day. It is vital to get quality deep sleep, but some factors may lead to reduced deep sleep.

sleeping cycle

Factors to reduce deep sleep

  • Smoking or drinking alcohol in the evening
  • Working night shifts, as it is hard to get quality deep sleep during the daytime
  • Being woken in the middle of the sleep cycle

REM sleep is as essential as deep sleep; this stage is playing a vital role for the mind and memory. At this time your brain consolidates all the information you have learned during the day, forms neural connections and replenishes its supply of neurotransmitters.

To get more mind-boosting sleep, try sleeping an extra 30-40 minutes in the morning when the REM stage is longer. Make sure you get enough sleep cycles, if you get less, your body will try to get more in-depth sleep, at the expense of REM sleep.

stages of sleep

How to get the most of your night sleep cycles?

Recent studies show that to feel refreshed, the critical factor is the number of complete sleep cycles and not the length of sleep.

If we were to sleep naturally and not to be disturbed, for example, by the alarm clock or full bladder, we would wake up, on the average, after a multiple of 90 minutes cycles – after 4.5 hours, 6 hours, 7.5 hours or 9 hours.

The person who sleeps only four cycles, which adds up to 6 hours, will feel more rested than someone who slept for 8 or 10 hours and did not let the brain to finish the 90-minute cycle.

Keep in mind the sleep cycles, when you will set the alarm tonight, try placing a wake-up time that’s a multiple by 90 minutes. For an example, if you go to bed at 10 pm, set your alarm for 5:30 (7,5 hours of sleep) instead of 6:00 or 6:30.

And you can use numerous “Sleep Cycle Apps” to track your heart rate and sleep cycles during the night.

How Does Your Sleep Cycle Change With Age?

Sleep changes throughout a person’s life.  From a newborn, through toddler years, school age, teenager and adulthood, sleep is changing.

sleep cycles at different age

Newborn (birth– approximately 4 months) They do not have distinctive sleep waves.  Sleep is categorized as “Active”, “Quiet” and “Indeterminate”. Active sleep is the equivalent to REM sleep and quiet sleep is equivalent to non-REM sleep.
A majority of the time, newborns are in active sleep which allows for frequent arousals or awakenings; this is necessary for regular periods of feeding.

Infants (Approximately 4 months – 1 year) Standard sleep stage distinction can be defined now.  Sleep becomes more stable and sleeping routines can be developed. Infants sleep about 10-13 hours per 24 hour period with 2-3 daytime naps.

Toddlers (1 year – 3 years)  Children spend approximately 25% in Stage 3 deep sleep with almost an equal amount of time in REM.  Average sleep time is 9.5-10.5 hours per 24 hour period. Typically naps will reduce to 1 per day.

Pre-School (3 – 6 years) Sleep time is similar to that of toddlers, approximately 9-10 hours per 24 hour period, with no afternoon naps. Stage 3 sleep still remains high in relation to total sleep time.

School Age (6 years – 12 years) Sleep time remains unchanged; 9-10 hours per 24 hour period and Stage 3 remains approximately 20-25% of total sleep time.  Restorative sleep is important for growth and development.

Teenager (12 years and beyond) Sleep time for teenagers is approximately 9-9.5 hours per 24 hour period.  There are physiological changes in circadian rhythm that occur causing sleep onset to be later. This internal shift is the cause for many young people to have the desire to want to “sleep in” in the morning.  As a person ages, the circadian rhythm shifts back and sleep again appears to regulate to approximately 6.5-8 hours of sleep per 24 hour period as an adult.

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