Sleep Well – Sleep Healthy Outreach Program

A Joint Public Health Education Initiative From The International Chiropractors Association And King Koil Sleep Systems

What is Sleep?

By Ronald M. Hendrickson, MSc.

Sleep is a universal experience of all humans and so it seems that we should not need to ask what sleep is.  While we all sleep and have a sense of what it is, few people understand how complex and vital to our health and performance sleep really is.  In fact, science is only beginning to delve into the many phases of sleep and how each dimension of sleep serves our physical and emotional needs.  What is universally agreed among researchers is that sleep is an absolutely vital component of health and that sleep problems are emerging as a major threat to public health in the 21stCentury.

Science understands sleep to be a naturally occurring state of physical and mental respite in which we suspend our active consciousness and where most external stimuli are blocked from the senses. One popular English language dictionary defines sleep as:  “…a naturally recurring state of relatively suspended sensory and motor activity, characterized by total or partial unconsciousness and the inactivity of nearly all voluntary muscles.”[1]

We remain subject to alarm and danger signals in terms of both noise and motion, but we transition into a unique state of quiet and rest for a significant period of time each day.  Science has also determined that sleep is an active period of heightened anabolic state, accentuating the growth and rejuvenation of the immune, nervous, skeletal and muscular systems. [2]

Sleep is an essential process:  Sleep is vital to the normal biological and psychological/emotional functions humans must engage in to survive.  Sleep enables the body and mind to rejuvenate, reenergize, and restore. Sleep allows the brain to perform vital tasks such as organizing long-term memory, integrating new information, and repairing and renewing tissue, nerve cells and other essential biochemicals.

How much sleep do we need? It is commonly and quite correctly said that we spend an entire third of our lives sleeping.  Sleep requirements vary significantly from person to person and different age groups have different requirements, but the vast majority of adults require six to eight hours of uninterrupted sleep per day.  Children need considerably more sleep per day in order to develop and function with newborns requiring up to 18 hours,[3] and then declining as a child ages, with 1 to 5 year olds needing from 12 to 14 hours and adolescents needing 9 to 10 hours.  Some sleep experts say that for adults, the best measure of how much sleep is needed is to determine how long a person needed to sleep to feel rested, refreshed and able to perform throughout a normal working day without feeling overly tired or in need of interim sleep.

Science is finding that the amount of sleep a person needs does not decrease with age. The reality is that sleep patterns and circadian rhythms change as one ages. Infants spend 50% of their sleep time in non-REM sleep and 50% in REM sleep; it has been shown that deep sleep coincides with the release of growth hormones, necessary for growing children. Adults spend approximately 20% in REM sleep, while elderly people may spend only 15% in REM sleep. Older adults tend to spend most of their sleep time in Stage 1 of non-REM sleep. Consequently, they have less REM sleep and report frequent awakenings.

Brain waves:  Much discussion of what happens when we sleep is done in terms of brain waves. Brain waves refer to measurements taken by a process called electroencephalography(EEG).  EEGs record the electrical activity within the brain,[4]recording the findings on a graph.

What happens when we sleep?  Healthy, restorative, normal sleep is characterized by a general decrease in body temperature, blood pressure, breathing rate, and most other bodily functions, but do not be mistaken, sleep is a very active period for the unconscious brain.  Research has proven that the brain is as active during sleep as it is when awake. Science has also established that we sleep in what are called “sleep cycles”.  Throughout an eight-hour period of sleep, a normal adult alternates between two very different states, non-REM and REM (Rapid Eye Movement) sleep which occur in four distinct stages.  REM sleep is the deepest level of sleep and is also often referred to as “dream sleep” since it is in this phase of deep sleep that the majority of dreaming activity takes place. Non-REM sleep consists of the first four stages of lighter sleep, from light dozing to near-deep sleep. Throughout this state of sleep, muscle activity is still functional, breathing is low, and brain activity is minimal. Approximately 75% of the sleep cycle is spent in non-REM sleep.

Most dreaming takes place during REM. Periodic eyelid fluttering takes place, thus the designation “Rapid Eye Movement.” We also experience various levels of muscle paralysis, irregular breathing with both respiration and heart rates speeding up,[5]as well as temperature shifts and slight blood pressure changes during REM sleep.  REM sleep has also been called “paradoxical” sleep because brain wave activity is similar to that registered in an awakened state. During REM sleep, the brain blocks signals to the muscles to remain immobile so dreams are not acted out. “The percentage of REM sleep is highest during infancy and early childhood, drops off during adolescence and young adulthood, and decreases further in older age.”[6]Adults spend about 20 – 25% of their sleep cycle in REM sleep.  Non-REM and REM sleep take place one after the other in four to five approximately 90-minute cycles. These four to five cycles are where the 7.5 to 8 hours as the required amount of sleep for the average person originates.

Stage 1:  Most of us are aware that as we move towards sleep, we begin to become drowsy; relaxed but still conscious, and then we “drift” off into a light state of sleep. This is what is commonly referred to as Stage 1.  For the average adult, it is estimated that only about 5% of non-REM sleep takes place here since it is the doorway to more complete sleep. Although the muscles and breathing rate begin to relax, it is very light “almost sleep” and one can be disturbed or awakened very easily.

Stage 2:  “Stage 2 is the predominant sleep stage during a normal night’s sleep.”[7]  Here is where a full state of sleep is believed to begin.  Approximately 45% of non-REM sleep is spent in Stage 2. Eye movement stops and brain waves slow down and become larger. Here, the brain engages in two very interesting functions.  The first is called “sleep spindles.”  This function is where the brain engages in bursts of what are called sigma bands or sigma waves that only last for a half to one and a half seconds, but seem to function to help keep a person in a sleep state by inhibiting the brain from responding to slight perceptions of light, noise or movement.  These bursts of waves keep the sleeper in a tranquil state, thus allowing them to move into deeper phases of sleep.

The other Stage 2 brain wave function is called a K-complex. Unlike the short, narrow waved of the sleep spindle, a K-complex is a wide swing of brain waves that is characterized by a sharp downward component followed by a slower upward component and lasts more than .5 second. The K-complexes are thought to have two functions; to help keep the sleeper in a tranquil state thus supporting the sleep spindle function, and to help with memory consolidation.[8]

Stage 3:  As sleep advances progressively deeper, an individual becomes difficult to arouse. A person spends approximately 12% of non-REM sleep in this stage. Actual slow brain-wave sleep begins as large and slow delta waves intermingle with smaller, faster ones.  This stage of sleep is characterized by 20 to 40% of slow wave (delta) sleep.

Stage 4:  Stage 4 is characterized by very deep sleep. Of the roughly 75% of non-REM sleep, approximately 13% is spent in this final stage. A person in one of the two latter stages, either 3 or 4, is harder to wake than a person in Stage 1 or 2. People who wake during deep sleep often feel groggy and disoriented for several minutes. By the time a person shifts into Stage 4, the brain produces delta waves almost exclusively.  Greater than 50% of Stage 4 Sleep is characterized by delta waves.

It takes between 30 to 40 minutes to cycle through the three stages of deeper sleep – Stages 2 through 4, eventually reaching a REM sleep phase. This cycle repeats itself 4 or 5 times each night.

What is the Body Clock?  Humans have a biological coordinating mechanism called the circadian rhythm, also known as the biological or body clock. The normal human 24-hour life cycle is termed “circadian.”  Functions governed by the body clock or circadian rhythm include body temperature, certain cellular functions such as repair and new-cell development as well as certain hormone production periods.  Sensors in the brain called “suprachiasmatic nuclei” (SCN) regulate our circadian rhythm. These sensors are triggered by or are at least very responsive to light and dark which help explain the night as the normal, natural period for sleep.

Why is Sleep Important?  Sleep is essential to a person’s physical and emotional well being.  Without an adequate amount of healthy, restorative sleep, our performance begins to suffer and with extensive sleep deprivation, we can exhibit seriously impaired performance, become much more likely to become sick, and our ability to function on all levels declines dramatically.  Studies of sleep and sleep deprivation suggest that the functions of sleep include recovery at the cellular, network, and endocrine system levels, energy conservation and ecological adaptations, and a role in learning and synaptic plasticity.  What this means in more simple terms is that the lack of healthy sleep impacts every function and every system in the body and today’s world is making it harder and harder to maintain a healthy sleep level.  Issues as different as school performance[9]and traffic safety are impacted by lack of sleep.  Studies show that sleep issues seriously impair a child’s learning ability, and we are all familiar with the all too common “falling asleep at the wheel” of a motor vehicle as a cause lf many traffic accidents.

Time to pay close attention to your personal sleep needs: The lack of sufficient healthy sleep is manifesting in a host of serious health consequences and health care professionals and consumers alike are starting to wake up to the need to pay close attention to the science of healthy sleep and the personal behavior patterns that can better support this vital health function.  Make adequate sleep a priority.  Use the Internet and resources like the International Chiropractors Association and King Koil to learn more about how you can make the right decisions about your schedule, diet, caffeine consumption, stress management and your sleep environment to establish a healthy sleep schedule.  By making healthy sleep a personal priority for yourself and your family, you will strengthen your ability to perform at work, at school, in sports, socially and most important of all, you will help your body stay healthy.


[1]Macmillan Dictionary for StudentsMacmillan, Pan Ltd. (1981), page 936.


[3]de Benedictis, Tina, PhD; Heather Larson, Gina Kemp, MA, Suzanne Barston, Robert Segal, MA (2007). “Understanding Sleep: Sleep Needs, Cycles, and Stages”, http://www.helpguide.org/life/sleeping.htm.

[4]Niedermeyer E, Lopes da Silva F (2004).Electroencephalography: Basic Principles, Clinical Applications, and Related Fields. Lippincott Williams & Wilkins.

[5]Baust, W., and B. Bohnert.The regulation of heart rate during sleep. Exp. Brain Res.7: 169-180, 1969

[6]“Overview, Waking, Non-REM, REM, Sleep Cycle, Factors, Age,” Original Date of Publication: 01 Dec 2000, Reviewed by: Stanley J. Swierzewski, III, MD, Last Reviewed: 04 Dec 2007,


[7]Benbadis, Selim R., MD,Rielo, Diego MD,“Normal SleepEEG,” http://emedicine.medscape.com

[8]Cash SS, Halgren E, Dehghani N. et al., (2009) Human K-Complex Represents an Isolated Cortical Down-State. Science, 324:1084-87 doi:10.1126/science.1169626

[9]a Ronald E. Dahl, “The impact of inadequate sleep on children’s daytime cognitive function, “Seminars in Pediatric Neurology, Pages 44-50, March 1996.

9.b Breus, Michael J, PhD, MD, “Back to School, Back to Sleep: Fixing your children’s sleep problems may improve their grades and their behavior,”   www.WebMD.com.


The International Chiropractors Association is presently engaged in a comprehensive review of sleep research with the aim of making those findings available to chiropractic practitioners worldwide.  We also believe that this review of the current state of sleep research will point to areas of where additional study is needed and, in cooperation with our affiliated educational institutions and with the support of our sleep products partner King Koil, we hope to help fill such gaps in sleep knowledge.  For more information contact ICA at chiro@chiropractic.org, TEL. 01-703-528-5000.






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