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SLEEP

INTRODUCTION

Sleep is a behavioral and neurobiological state which is characterized by a change in the state

of consciousness and bodily as well as neurological behavior. Sleep is an involuntary periodic

process which is dependent on environmental and internal circumstances of an individual. Sleep

is divided into REM (Rapid Eye Movement) sleep and NREM (Non-Rapid Eye Movement)

sleep based on varied characteristics. The different characteristics of the neurobiological states in

humans (which are wakefulness, REM sleep and Non-REM sleep) are distinguished by:

Environmental Responsiveness.

General Physiology.

EEG waveforms (of muscle and eye movement).

Muscle tones.

Mental activity.

PRINCIPAL CHARACTERISTICS OF REM SLEEP AND

NON-REM SLEEP

REM SLEEP SLOW-WAVE/NREM SLEEP

EEG De-synchrony (irregular, rapid waves) EEG Synchrony (slow waves)

Lack of Muscle Tones Moderate Muscle Tones

Rapid Eye Movement Slow or Absent Eye Movement

Genital Activity Lack of Genital Activity

Dreams -

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PHYSIOLOGICAL MECHANISM OF SLEEP

The natural cycle of sleep and wakefulness is regulated by the nervous system.

Suprachiasmatic nucleus is a structure in the hypothalamus which is specifically involved in the

regulation of circadian rhythms (brain wave rhythms, hormone production, cell regeneration,

etc). The hypothalamus secretes various hormones which influence the sleep and wake state of

mind. These are various neurohormones and neurotransmitters which are linked with and

encourage sleep like melatonin, which promotes sleep, and adenosine, which accumulates during

wakefulness, encouraging sleep, and then decreases during sleep. Other areas of the brain such as

medulla and thalamus also control sleep and arousal.

Benington, Kodali and Heller (1995) suggested that a nucleoside neurotransmitter,

adenosine, could be one of the primary controlling agents of sleep. Glucose is supplied by blood

to the brain when cognitive activities take place. But when blood fails to provide the required

amount of glucose due to high activity of the brain, Astrocytes provide the needed nutrition in

form of glycogen. The increase in the level of the metabolism of glycogen increases the levels of

adenosine. This increase of adenosine increases the amount of delta activity during sleep. Recent

researches also verify the hypothesis of adenosine as a mechanism which regulates sleep.

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FUNCTIONS OF SLEEP

Sleep is one of the intrinsic needs of living organisms. Sleep is inevitable and is an

involuntary behavior. The function of sleep is still not fully known but most researchers believe

that the primary function of NREM sleep is to provide the brain with rest while REM sleep

supports brain development and learning.

FUNCTIONS OF SLOW WAVE SLEEP

Effects of Sleep Deprivation:

In 1978, Horne conducted over 50 experiments of sleep deprived people. The reports

indicated that sleep does not affect the physical performance of the body but the affect of sleep

on the cognitive abilities were witnessed. Some subjects reported of hallucinations, perceptual

distortions and difficulty in concentration. Further research found out how during stage 4 of

slow-wave sleep the presence of delta activity in particular regions of the brain indicated

relaxation and rest in that area of brain. Thus, it could be stated that one of the primary function

of slow-wave sleep is to provide the brain with rest and allows the brain to recover from the

day’s activities.

Effects of Exercise on Sleep:

The studies conducted by Adey, Bors and Porter in 1968 and Ryback and Lewis in 1971

highlighted the relationship between sleep and exercise. These studies focused on the role of

sleep to restore physiological function. The results indicated that though there isn’t a very strong

relationship between sleep and exercise, the hypothesis is still acceptable and it can be said that

one of the functions of sleep, even though not primary, could be to provide the body with rest.

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Effects of Mental Activity on Sleep:

The studies of Roland in 1984, Horne and Minard in 1985, and Kattler, Dijk, Borbely in

1994 signify the strong correlation of mental activity and sleep. After the subject was exposed to

tasks requiring mental activity and alertness, glucose metabolism significantly increased in the

frontal lobes of the brain. During the 4th stage of slow-wave sleep delta activities are most

prevalent in the frontal lobes allowing that particular part of the brain to relax. Also, the study

showed that increase in mental activity resulted in increase in the duration of stage 4 slow-wave

sleep.

FUNCTIONS OF REM SLEEP

The functions of REM sleep are less understood than slow-wave sleep and the studies

conducted present inconclusive results. The studies conducted by various researchers show that

REM sleep helps in the development of brain. According to Greenberg and Pearlman (1974),

emotionally related memories of events of the previous day are strengthened and merged with

existing memories during REM sleep. Other researchers oppose this hypothesis. Crick and

Mitchison (1983, 1995) suggest that REM sleep discards unwanted memories during REM sleep

to prevent the clustering of unwanted information. REM sleep is also thought to promote

learning. Studies like the increase in the duration of REM sleep of college students during

examinations and less REM sleep requirements of children with mental retardation as compared

to normal children highlight the hypothesis of the strong relationship between REM sleep and

learning.

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STAGES OF SLEEP

Sleep may seem like constant state of rest for mind and body but it consists of various

stages. Sleep stages are measured by gross brain waves, muscle tones and eye movement. The

cycle of different sleep stages lasts about 90 to 100 minutes. A normal individual will experience

the complete cycle 4 to 5 times. The sleep cycle begins with stages of slow brain wave sleep

called Non-REM sleep. The other state of sleep called REM sleep differs from other phases of

sleep (Non-REM) due to its physiological nature. There is rapid eye movement which can be

witnessed in REM sleep. Dreaming occurs during all stages but the ones that are clearly recalled

take place during REM sleep. REM sleep is also called paradoxical sleep as the activities of the

brain’s neurons are quite similar to those of the waking hours.

The sleeping pattern changes with age but a normal adult experiences 20 to 25 percent of

REM sleep during their total sleep and Non-REM sleep occupies 75 to 80 percent of total sleep.

The time distribution of sleep of a normal adult:

NREM (75%)

Stage 1 – 5%

Stage 2 – 45%

Stage 3 – 12%

Stage 4 – 13%

REM (25%)

STAGES OF NON-REM SLEEP

STAGE 1: This is the initial stage of sleep in which the sleeper “drifts off” and enters a period

which could be called the “twilight time”. The brain waves become slower, smaller and

somewhat irregular. The sleep is distinguished by drifting thoughts and dreams that move from

real to fantastic. The sleeper could be easily awakened and deny having slept. This stage of sleep

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lasts about 10 minutes in most sleepers. The bodily functions which take place during stage 1 of

Non-REM sleep defines the characteristics of Non-REM sleep. The characteristics are:

Breathing becomes slow and even.

The heartbeat becomes regular.

Blood pressure falls.

Brain temperature decreases.

Blood flow to the brain is reduced.

Little or no body movement. (Anonymous, 2007)

STAGE 2: This is the intermediate stage of sleep and lasts about 20 minutes in most sleepers.

The sleeper falls deeper into sleep, gradually becomes less aware of the external environment

and progressively becomes harder to awaken. The characteristics of stage 2 are:

Larger brain waves and occasional quick bursts of activity.

The sleeper will not see anything even if the eyes are opened.

Bodily functions slow down.

Blood pressure, metabolism, secretions, and cardiac activity decrease. (Anonymous,

2007)

STAGE 3: This stage of sleep lasts up to 30 to 45 minutes after falling asleep. It is the beginning

of deep sleep. It becomes harder to awaken the sleeper and requires an active effort. Stage 3 is

characterized by slow brain waves (at the rate of 0.5 to 4 per second). The brain waves also

become quite large, at least five times the size of waves in Stage 2. These brain waves are known

as delta waves.

STAGE 4: Deepest sleep takes place in this stage. The first period of this deep sleep is the

deepest and if awaken during this stage, the sleeper may experience “sleep drunkenness” and

would be disoriented and unable to function normally for a small period of time. Stage 4 is

characterized by:

The brain waves (called delta brain waves) are quite large.

The sleeper experiences virtual oblivion. If the sleeper is a sleepwalker or a bed-wetter,

those activities will begin in this phase

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Bodily functions continue to decline to the deepest possible state of physical rest.

(Anonymous, 2007)

REM SLEEP

During the REM stage of sleep, brain activity becomes more active while the body is

paralyzed of any voluntary muscle movement. Non-REM is a progressive state of relaxation but

during REM sleep body functions perk up constantly. The characteristics of REM sleep are as

follows:

Brain waves are small and irregular, with big bursts of eye activity. The brain wave

activity at this time resembles waking more than it does sleeping.

Blood pressure may increase drastically.

Pulse rates increase in an irregular way.

Breathing becomes irregular and oxygen consumption increases.

The chin is relaxed during REM sleep.

The face, toes and fingers may twitch.

The sleepers' large muscles are literally paralyzed.

They cannot move their torsos, arms, or legs.

The body seems to have abandoned its effort to regulate its temperature during the REM

phase.

Shivering and sweating cease at this time, and the body's temperature drifts gradually

toward the temperature of its environment.

EEG PATTERNS AND NEUROBIOLOGICAL STATES

EEG patterns of brain activity differentiate the neurobiological states of human based on the

following brain activities:

Alpha activity: Regular, medium frequency waves of 8-12 Hz.

Beta activity: Irregular, low-amplitude waves of 13-30 Hz.

Theta activity: High-amplitude waves of 3.5-7.5 Hz.

Delta activity: Regular, Synchronous waves of less than 4 Hz.

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Wakefulness consists of desynchronized beta activity. Relaxation and drowsiness consists of

alpha activity. Stage 1 sleep is a transitional period which consists of alternating periods of alpha

activity, irregular fast activity and theta activity. Stage 2 sleep consists of sleep spindles (short

burst of waves of 12-14 Hz.) and k complexes (sharp, sudden wave forms) and lacks alpha

activity. Stage 3 sleep contains 20-50% delta activity and stage 4 sleep consists of more than

50% delta activity. These stages of sleep of slow-wave sleep (NREM sleep) differs from REM

sleep because NREM sleep has the above mentioned synchronized brain wave activities while

REM sleep has desynchronized, rapid and irregular waves.

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DISORDERS OF SLEEP

On an average we, human beings spend one-third of our lives sleeping, thus, any disturbance

in our sleep will affect our quality of life. According to the Diagnostic and Statistical Manual of

Mental Disorders 4th Edition Test Revised, the sleep disorders are organized into four major

categories on the basis of their etiology or causal factors. The four major categories are under:

1. Primary Sleep Disorders

2. Sleep Disorders Related to Another Mental Disorder

3. Sleep Disorder Due to a General Medical Condition

4. Substance-Induced Sleep Disorder

PRIMARY SLEEP DISORDERS

Primary Sleep Disorders are those disorders whose etiologies (causes) are unknown and

also doesn’t fall into the other three categories of Sleep Disorders i.e., another mental disorder,

general medical condition and substance induced.

Primary Sleep Disorder are presumed to arise from endogenous abnormalities in sleep-wake

generating or timing mechanism, often complicated by conditioning factors.

Furthur the Primary Sleep Disorders can be broadly characterized into two categories namely

Dysomnias

Parasomnias

These categories of Primary Sleep Disorders further comprises of various sleep disorder which

fall into one of the two depending on their nature and cause.

DYSOMINAS:

Dysomnias are characterized by abnormalities in the amount, quality or timing of sleep.

Under Dysomnias the sleep disorder that fall into it according to DSM-IV-TR are as follows:

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Primary Insomnia – characterized by difficulty in initiating or maintaining sleep, or non-

restorative sleep.

Primary Hypersomnia – characterized by excessive sleepiness as evidenced by either

prolonged sleep episodes or daytime sleep episodes.

Narcolepsy – characterized by irresistible attacks of refreshing sleep.

Breathing-Related Sleep Disorder – characterized by sleep disruption, leading to

excessive sleepiness or insomnia that is judged to be due to a sleep-related breathing

condition.

Circadian Rhythm Sleep Disorder (formerly known as Sleep-Wake Schedule Disorder) –

characterized by a persistent or recurrent pattern of sleep disruption leading to excessive

sleepiness or insomnia that is due to mismatch between sleep-wake schedule required by

a person’s environment and his or her circadian sleep-wake pattern.

Subtypes:

Delayed Sleep Phase

Jet Lag type

Shift work Type

Dysomnias Not Otherwise Specified – all the disorders that fail to meet the criteria for the

above mentioned disorder will come under this category. The disorders under this

category will display some of the symptoms of the above mentioned disorder but not all.

PARASOMNIAS:

Parasomnias are characterized by abnormal behavior or physiological events occurring in

association with sleep, specific stage of sleep stages or sleep-wake transitions.

Under Parasomnias the sleep disorder that fall into it according to DSM-IV-TR are as follows:

Nightmare Disorder (formerly Dream Anxiety Disorder) – characterized by repeated

awakenings from the major sleep period or naps with detailed recall of extended and

extremely frightening dreams, usually involving threats to survival, security or self-

esteem. The awakenings generally occur during the second half of the sleep period.

Sleep Terror Disorder – characterized by recurrent episodes of abrupt awakening from

sleep, usually occurring during the first third of the major sleep episode and beginning

with a panicky scream.

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Sleepwalking Disorder – characterized by repeated episodes of rising from bed during

sleep and walking about, usually occurring during the first third of the major sleep

episode.

Parasomnias Not Otherwise Specified - all the disorders that fail to meet the criteria for

the above mentioned disorder will come under this category. The disorders under this

category will display some of the symptoms of the above mentioned disorder but not all.

SLEEP DISORDERS RELATED TO ANOTHER MENTAL

DISORDER

Sleep Disorders Related to Another Mental Disorder involves a prominent complaint of

sleep disturbance that result from diagnosable mental disorder, most commonly Mood Disorder

and Anxiety Disorder, but that is sufficiently severe to warrant an independent clinical attention.

According to DSM-IV-TR the disorders that further fall under this category are as follow:

Insomnia Related to Another Mental Disorder – characterized by presence of insomnia

that is judged to be related temporally and causally to another mental disorder.

Hypersomnia Related to Another Mental Disorder– characterized by presence of

hypersomnia that is judged to be related temporally and causally to another mental

disorder.

SLEEP DISORDER DUE TO A GENERAL MEDICAL

CONDITION

Sleep Disorder Due to a General Medical Condition involves a prominent complaint of

sleep disturbance that result from the direct physiological effects of a general medical condition

on the sleep-wake system.

According to DSM-IV-TR the subtypes are as follow:

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Insomnia type – refers to a sleep complaint characterized primarily by difficulty falling

asleep, difficulty maintaining sleep or feeling of non-restorative sleep.

Hypersomnia type – the predominant complaint is one of excessively long nocturnal sleep

or of excessive sleepiness during waking hours.

Parasomnia type – refers to a sleep disturbance characterized primarily by abnormal

behavioural events that occur in association with sleep or sleep transition.

Mixed type – a sleep problem due to general medical condition characterized by multiple

sleep symptoms but no symptom clearly predominates.

SUBSTANCE-INDUCED SLEEP DISORDER

Substance-Induced Sleep Disorder involves prominent complaints of sleep disturbance that

result from the concurrent use, or recent discontinuation of use, of substance which would also

include medication.According to DSM-IV-TR the subtypes are as follow:

Insomnia type – refers to a sleep complaint characterized primarily by difficulty falling

asleep, difficulty maintaining sleep or feeling of non-restorative sleep.

Hypersomnia type – the predominant complaint is one of excessively long nocturnal sleep

or of excessive sleepiness during waking hours.

Parasomnia type – refers to a sleep disturbance characterized primarily by abnormal

behavioural events that occur in association with sleep or sleep transition.

Mixed type – a substance induced sleep problem characterized by multiple types of sleep

symptoms but no symptom clearly predominates.

Specifiers:

With Onset During Intoxication – This specifier should be used if criteria are met for

intoxication with the substance and symptoms develop during the intoxication syndrome.

With Onset During Withdrawal – This specifier should be used if criteria are met for

withdrawal from the substance and the symptoms develop during or shortly after a

withdrawal syndrome.

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As mentioned above the Substance-Induced Sleep Disorder most commonly occur either during

intoxication or as a result of withdrawal from the substance. The different types of substances

that can bring about sleep disturbance thus warranting some clinical attention or may be

diagnosed as Substance-Induced Sleep Disorder are as follows:

Alcohol

Amphetamines

Caffeine

Cocaine

Opioids

Sedatives

Hypnotics

Anxiolytics

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CAUSES AND TREATMENTS OF

SLEEP DISORDERS

CAUSES

Sleep disorders are more prevalent in older adults due to aging and the physiological changes

that take place because of that. But other causes of disturbances in sleep pattern are:

Illness

Medication

Caffeine

Stress

Anxiety

Depression

Lack of activity

Poor sleep habits

Sleep disorders like insomnia, at any age, is worsened by self-defeating actions like

ruminating over it, counting the numbers of hours slept and those spent waiting to fall asleep and

medications taken to deal with them.

TREATMENTS

Sleeping pills are the most commonly used treatment for sleep disorders. Though the

consumption of sleeping pills may seem appropriate, the drug gradually loses its effectiveness

and continuous use can even make sleep light and fragmented. Continuous use of these

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medications could bring about a condition called drug-dependent insomnia. It could also cause

difficulty in learning and thinking clearly the following day.

Alcohol, a central nervous system depressant, does induce relaxation and drowsiness

helping the individual fall asleep but alcohol has its negative effects on the architecture of sleep.

Alcohol reduces REM sleep causing individuals to feel tired and unable to think clearly the next

day. Also, dependency is one of the main issues related to alcohol which can be caused due to

the increased intake of it.

Intervention and explanation of the nature of sleep and the underlying problem by a

therapist can help improve sleep. Worry and fear regarding sleep could worsen sleep patterns

thus the proper explanation that lack of sleep is not a calamity and it would not cause irreversible

brain damage or mental illness, like some individuals fear, can help these individuals relax and

worry less about sleep, resultantly sleeping better.

Relaxation training and regular healthy exercise can help individuals develop good

sleeping habits and train them to fall asleep. Waking up at the same time in the morning,

avoiding activities that disrupt sleep patterns, lying down only at the time of sleep, etc are some

trainings that could help patients cope with their sleep disorder.

Cognitive-behavioral intervention, a non-pharmacological treatment, for sleep

difficulties has gathered much positive responses over the years. Studies have shown that these

interventions have superior long lasting effect as compared to drug therapies. The behavioral

treatment includes education about sleep hygiene, correction of faulty expectations and beliefs,

the teaching and practicing of good sleep habits and relaxation treatment.

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REFERENCES

Davidson, G.C., Neale, J.M., & Kring, A.M. (2002). Abnormal psychology. (9th ed). USA: Wiley

& Sons.

Carlson, N.R. (2005). Foundations of physiological psychology. (6th ed.). India: Dorling

Kindersley.

American Psychiatric Association. (2000). Diagnostic and statistical manual of mental

disorders: DSM-IV-TR. Washington, DC: American Psychiatric Association.

Buysse, D.J. (2005). Sleep disorder and psychiatry. USA: American Psychiatric Publication.

Sadock, V.A., & Kaplan H.I. (2008). Kaplan & Sadock's concise textbook of clinical psychiatry.

(3rd ed.). UK: Lippincott Williams & Wilkins.

Anonymous. (2007). Sleep. Retrieved March 14, 2009 from

http://www.holisticonline.com/Remedies/Sleep/sleep_stages-REM.htm

Anonymous. (2007). Sleep. Retrieved March 14, 2009 from

http://www.holisticonline.com/Remedies/Sleep/sleep_stages-1-4NREM.htm