Sleep cycles are regulated by our body clock. Each cycle has specific sleep stages, each vital for your body. Understanding these sleeping needs, cycles and stages can help you get better sleep.

The Body's Sleep Controllers

The bodies need for sleep is controlled by two functions: the circadian clock and adenosine.

Circadian Clock

The need for sleep is controlled by an internal circadian clock that regulates when it is time to sleep and time to wake. This clock is driven by daylight and time of day.

Adenosine

A chemical messenger, adenosine builds up during the day during our normal energy consuming resources. The more energetic we are, the more adenosine that builds up in the brain, and the sleepier we feel at the end of the day. This is why you always sleep particularly well after a days skiing or other high energy consuming activity.

Adenosine + circadian clock = a powerful sleep message to the body.

Sleep is essential for rejuvenation of both our minds and our bodies in many ways. Prolonged periods of inadequate sleep lead to:

Lower productivity - daytime drowsiness, trouble concentrating, irritability, increased risk of accidents.
Memory and Concentration Impairment - sleep helps to organize memories, solidify learning, and improve concentration.
Mood - actively dreaming [REM sleep], regulates mood that in turn impacts your emotions, social interaction, and decision making.
Motor skills - driver fatigue causes over 100,000 accidents and 1500 deaths each year.
Immune system - lowering your ability to fight off infections, colds and flues.
Nervous system - sleeptime is used to repair neurons. Neurons manage both voluntary commands, like moving your leg and involuntary commands such as breathing and digestion.
Brain cellular repair, replenishment and growth - sleep is used to replenish cell energy stores required to function normally, repair cellular damage and grow new nerve cells in the brain.
Hormone release - produced to trigger or regulate particular body functions, such as HGH [Human Growth Hormone] are released during sleep. HGH is vital for growth and restorative processes such as wound or muscle repair.

Types of Sleep

During sleep goes we cycle between deep restorative sleep and more alert stages and dreaming. As the night progresses, we spend more time in dream sleep and lighter sleep.

REM (Rapid Eye Movement) sleep is when you do most active dreaming. Your eyes actually move back and forth during this stage, which is why it is called REM sleep.
Non-REM (NREM) sleep consists of four stages of deeper and deeper sleep.

Each sleep stage is important for overall quality sleep, but deep sleep and REM sleep are especially vital.

Stages of Sleep

Stage 1 Drowsiness - lasts only 5 - 10 minutes. Eyes move slowly under the eyelids, muscle activity slows down, and you are easily awakened.

Stage 2 Light Sleep - Eye movements stop, heart rate slows, and body temperature decreases.

Stages 3 & 4 Deep Sleep - during this time it is difficult to wake you and if awakened, you do not adjust immediately and often feel groggy and disoriented for several minutes.

Chronic Sleep Deprivation

Chronic sleep deprivation is characterised by signs such as falling asleep as soon as your head hits the pillow, regularly need an alarm clock to wake up, and the need for frequent naps during the day.

It will also show up as:

Difficulty waking up in the morning
Increased confusion, clumsiness and forgetfulness
Falling asleep during work or class
Poor performance at work or sports
Difficulty making decisions
Excessive moodiness and irritation

Sleep deprivation can also cause long term changes to the body, contributing to increased risk of obesity, diabetes and heart disease.

How Much Sleep You Need

We all have different needs for sleep - they key is how you feel when you wake up. If you feel refreshed, chances are you’re sleeping enough. If not, you may be sleep deprived. The amount of sleep is governed by your age and genetics, how much exercise you do during the day and the quality of sleep.

As a guideline:

Infants - 16 hours a day
Babies and Toddles - 10 to 14 hours per day from a combination of nighttime sleep and naps.
Children [3 to 6] - 10 to 12 hours of sleep
Children [6 to 9] - 10 hours of sleep
Children [9 to 12] - 9 hours of sleep
Teenagers - 9 hours of sleep per night. Teens are biologically programmed to want to stay up later and sleep later in the morning, which doesn't fit with school schedules.
Adults - 7 to 8 hours a night
Older adults - 7-8 hours of sleep. However, this may be for shorter time spans, is lighter than a younger adult’s, and may include a nap during the day.
Pregnant women - may need more sleep at night and small catnaps during the day.

Sleep Debt

Prolonged inadequate sleep builds up a sleep deprivation account, or sleep debt. This debt leads to decreased mental and physical health.

Short term sleep debt - from 1 or 2 nights may be repaid within a day or twos improved sleep.
Long term sleep debt - will take longer - maybe a week or two before your body reverts to optimal sleep habits.

Using Sleep Cycles to Improve Sleep

Understanding sleep stages and the sleep cycle can help you get better sleep. We know the body clock is sensitive to light, time of day and other cues for sleep and that during sleep goes we cycle between deep restorative sleep and more alert stages and dreaming. As the night progresses, we spend more time in dream sleep and lighter sleep.

Deep Sleep Restoration

Deep sleep is the most vital stage and is the first stage that the brain attempts to recover when sleep deprived. It is during deep sleep that the brain restores the energy we expend during our waking hours. Blood flow decreases to the brain and redirects itself towards the muscles, restoring physical energy. Iimmune functions increase during deep sleep.

This restoration does not occur when you over indulge in substances such as alcohol and nicotine which disrupt deep sleep, or you are frequently disrupted by loud noises outside the home or caring for elderly or infants.

REM Sleep Restoration

REM or Dream Sleep starts about 70 to 90 minutes into your sleep cycle, with 3-5 REM episodes per night. During REM your emotional, memory and stress processing takes place. Breathing is rapid, irregular and shallow, the heart rate increases, blood pressure rises, sex organs swell in both males and females.

REM sleep is essential to our minds for learning and developing new skills. Dreams are commonly beliebed to be the the processing of unconscious desires and random fragments of information received during the day.

Improving your overall sleep will also increase your REM sleep. If your body is deprived of deep sleep, it will try to make that up first- at the expense of REM sleep.

Disrupted REM sleep will lead to your body attempting to get more REM the next night, leading in extreme cases to very vivid, almost hallucinating dreams.

Increasing your REM sleep helps boost your mood during the day. Since your sleep cycle delivers Deep Sleep first, try to sleep a little more in the morning to extend your REM sleep stage. Even an extra half hour to hour can improve your mood.

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