The Sleep Cycle
Sleep is definitely not the inactive state that many thought and still believe it to be. Technology is giving us tremendous insight into the dynamic behaviors that occur as we sleep.
For example, did you know that, during a particular stage of your sleep cycle, the body releases hormones it needs heal and rebuild? Also, did you know that during another stage, memories are transferred from short-term to long-term storage so that you can keep them?
If any of these stages in your sleep cycle are compromised, so are the benefits they provide.
The Sleep Cycle and the 4 Stages of Sleep
Your sleep cycle is punctuated by four unique and dynamic stages. After you complete your first sleep cycle, you begin another, and then another, and so on.
And, as you cycle your way through a night of sleep, these recurring cycles change in terms of length.
The stages of sleep are first differentiated by the movement of your eyes while sleeping. Starting in non-REM (non rapid eye movement) sleep, you have little-to-no eye movement. Then, its on to REM (rapid eye movement) sleep in which your eyes are active and dart about rapidly.
Non-REM sleep is further broken down into 3 sleep stages which are characterized by your brain activity. These stages are known as NREM1, NREM2 and NREM3 (or N1, N2 and N3).
Progressing from NREM1 to NREM3, your brain waves become slower. The NREM3 stage is referred to as “slow-wave” or “deep” sleep. Once you get to REM sleep, your brain is activated with waves similar to those while awake.
(Studies previous to 2007 had classified 4 stages of NREM. Since then, stages N3 and N4 have been combined and are now known as N3.)
Non-REM Sleep (or NREM sleep)
1. NREM1: Light sleep. Your brain transitions to unconsciousness with Theta waves
This is where you typically enter the sleep cycle. You drift in and out of sleep while your eye movements and muscle activity slows. If awakened during this stage, it was as if you never fell asleep.
In your brain, the wakeful and relaxing Alpha waves are replaced by Theta waves causing you to transition from alertness to unconsciousness.
During light sleep, sudden contractions such as hypnic jerks are common. Normally, this stage lasts about 5 to 10 minutes. If this stage is extended, it usually indicates a problem.
2. NREM2: Light sleep. Your movements cease as the brain produces sleep spindles
Your body further prepares itself for sleep by slowing its heart rate and lowering its temperature. Eye movements cease, however you can still easily be awakened.
Your body produces bursts of brain activity called sleep spindles. These spindle waves are thought to help turn off brain “noise” and induce tranquility.
This stage generally lasts from 10 to 25 minutes. Dreaming is typically nonexistent during light sleep.
3. NREM3: Deep Sleep (or Slow Wave Sleep). Delta waves promote slow-wave sleep and healing hormones
Deep sleep is considered to be the most restful of the 4 stages of sleep. Your eyes do not move, there is little to no muscle activity, and your heart rate is steady. If awakened from deep sleep, you will be disoriented.
Your brain produces slow Delta waves which stimulate the release of several growth hormones. These hormones help to heal and rebuild your body. They also help strengthen the immune system.
This stage typically lasts between 20 and 40 minutes. Dreams are common during deep sleep, although not as common or as vivid as dreams from REM sleep. It is during this slow-wave sleep that most parasomnias such as sleepwalking, night terrors and sleep hallucinations occur.
As you age, this critical stage of deep sleep becomes less and less attainable. Also, alcohol consumption can wreak havoc on this stage. Insomnia and sleep deprivation can become a concern if you can not attain enough deep sleep.
4. REM sleep. Your brain is highly activated with beta waves
REM sleep comes next. Your muscles are temporarily paralyzed, yet your eyes dart about rapidly. Your heartbeat and body temperature become unregulated. Breathing is frequent and shallow. Awakening from REM sleep is more difficult than during any other stage.
During REM sleep, your brain is energized with Beta waves that are similar to those while awake. REM is considered the “learning” stage of the sleep cycle. The brain is stimulated and your cognitive processes – including attention, memory, comprehension, judgement, reasoning, etc – are processed and consolidated.
The REM stage typically occurs about 70 to 90 minutes into the sleep cycle. The first REM stage lasts about 10 minutes, and it is the shortest of the night. The final REM stage in the morning may last up to an hour.
Considered the dream stage, REM can produce intense dreams because of the increased brain activity. Awakening while in REM can cause disorientation as well as cut short the important cognitive processes that keep you sharp.
Once you transition through these four stages of sleep, you start with another cycle.
The Sleep Cycle: When to Wake Up
Awakening during the “light sleep” stages of the sleep cycle ensures that you are more alert and refreshed when you get out of bed.
If you are jolted awake while in REM sleep (which is often the case with a traditional alarm clock) you usually start your morning a little disoriented and confused. Not only are your dreams interrupted, your brain’s other important processes are short-changed. For example, you cut short the consolidation and long-term storage of important memories.
Fortunately, new technology provides us with smart sleep alarms. These innovative devices are capable of waking you at an optimal time during your sleep cycle. You simply set a preferred window of time and the device identifies the optimal time based on your sleep stage to awaken you.
How Long is a Sleep Cycle?
The average length of your first complete sleep cycle is about 70 to 100 minutes. After the initial cycle, the following cycles are typically a bit longer, averaging about 90 to 120 minutes.
Each sleep cycle is a little different than the previous one. For example, you usually spend more and more time in REM with each new sleep cycle. You also spend less time in NREM3, or “deep sleep”. So, by the morning hours, your cycles usually include about an hour of REM sleep, with little-to-no “deep sleep”.
Innovative sleep trackers can now easily capture this sleep cycle information by stages and then provide it to you in easy-to-understand graphical formats.
Knowing and adjusting for the length of your sleep cycles can help to wake up more energized and refreshed. Working backwards, you can set a bedtime that coincides with an optimal wake time.
How to Reset Your Sleep Cycle
If normal sleep has been disrupted or if you suffer from a sleep disorder such as delayed sleep phase syndrome, you may wish to reboot your sleep cycle.
In order to reset your sleep cycle, experts recommend the following strategies:
- Develop a routine – and follow it consistently. This includes a bedtime and wake-up time. Your body thrives on regularity.
- Brighten your morning – by getting natural light as early as possible. Sunlight is one of the strongest triggers of your body’s sleep-wake cycle..
- Dim your nighttime environment – to naturally prepare your body for sleep. The lack or bright and blue light initiates natural sleep hormone production.
- Exercise – in the morning or early afternoon. Studies show that workouts significantly boost sleep quality.
- Control your food, alcohol and caffeine intake – as well as sleep environmental factors.
Pay close attention to sleep hygiene, as these practices have the most effect on your sleep-wake cycles.
What are Alternative Sleep Cycles?
In the West, we tend to stick to a single sleep cycle. This simply means we sleep for a longer period at night, a system called monophasic sleep. A growing movement towards alternate sleep cycles include polyphasic sleep.
The most common form of polyphasic sleep is the afternoon nap. Many Mediterranean cultures have carried on with the tradition of an afternoon nap and now the idea is catching on in the Western World as well.
Afternoon naps typically last about 90 minutes which is time enough for a full sleep cycle. Advocates claim that naps improve focus and enhance the quality of sleep.
Other options for polyphasic sleep:
- Uberman Cycle –includes several 30 to 40 minute naps throughout the day. This is considered the most radical in that the naps do not allow time for a full sleep cycle.
- Everyman Cycle – centered around one larger chunk of sleep (around 90 minutes) per day supplemented by several 20 minute naps throughout the day.
- Dymaxion Cycle – features a 30-minute nap every 6 hours for a total of 2 hours of sleep per day.
At this time however, none of these options are as popular as the afternoon nap.Share This: