OVERVIEW OF SLEEP

RITU G. GREWAL, MD

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Key to Evaluation of Sleep Problems

• Sleep Physiology

• Factors that impact on sleep

• Sleep History

• Polysomnogram

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Defining Sleep• Sleep physicians define human sleep on the basis of a

person’s observed behavior (reclined position, closed eyes, decreased movement, decreased responsivness to stimuli)

• and accompanying physiologic changes in brain’s electrical activity

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SLEEP REST

Differentiating Sleepiness from Tiredness or Fatigue

• A tired or fatigued individual does not necessarily have a propensity to fall asleep given an opportunity to do so.

• A sleepy individual is not only anergic but will fall asleep given the opportunity to do so.

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Responsiveness to Stimuli is Not Completely Absent in Sleep

• a sleeper continues to process some sensory information during sleep

• meaningful stimuli are more likely to produce arousals than non-meaningful ones• sound of one’s own name is more likely to arouse than other

sounds• cry of her baby is more likely to arouse a sleeping mother than

a cry of another infant.

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Sleep • Active• Complex• Highly Regulated• Involves different neuronal groups • Purpose is not understood• Essential • Composed of two fundamentally different states : REM

sleep & NREM sleep

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Sleep consists of two strikingly different states• non-rapid eye movement sleep (NREM)

• “shallow” NREM stage 1 (start of sleep)• “deeper” NREM stages 2• “deepest”3 (slow wave sleep)• brain is regulating bodily functions in a movable body

• rapid eye movement sleep (REM)• highly activated brain in a paralyzed body• first brief episode of REM follows NREM in

approximately 90 minutes

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Normal Sleep Histogram

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How Much Sleep Does One Need?

• One needs sufficient sleep to feel alert, refreshed, and avoid falling asleep involuntarily during the waking hours.

• Most young adults average between 7 and 8 hours of sleep nightly, but there is a significant individual and night to night variability

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Three States of Being

• Wake

• REM Sleep

• Non-REM Sleep

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• The Cyclic alteration of these three states defines two sleep rhythms

• CIRCADIAN RHYTHM

• ULTRADIAN RHYTHM

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Two Drives Regulating Sleep

• Sleep is regulated by the two basic processes:• homeostatic process, which depends on the amount

of prior sleep and wakefulness• circadian process, which is driven by an endogenous

circadian pacemaker, generating near 24-hour cycles of behavior.

• The interaction of homeostatic and circadian processes helps to maintain wakefulness during the day and consolidated sleep at night

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Homeostatic Factor

• Virtually all organisms have an absolute need to sleep. • Humans cannot remain awake voluntarily for longer

than two – three days• rodents cannot survive without sleep for longer than

few weeks.

• The homeostatic factor represents an increase in the need for sleep, “sleep pressure”, with increasing duration of prior wakefulness.

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Homeostatic Regulation of Sleep

• When normal sleep is preserved, • homeostatic factor represents a basic increase in

sleep propensity during waking hours

• When a normal amount of sleep is reduced, • the homeostatic drive is increased • leading to increased sleep pressure and sleepiness

during the day

• The pull of this drive builds up during wakefulness and reaches its peak at sleep time

• Its strength declines during sleep with lowest point

upon awakening in the morning

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Adenosine and Homeostatic Sleep Drive

• A number of endogenous sleep producing substances mediate the transition from prolonged wakefulness to NREM sleep. • Adenosine mediates this transition by inhibiting arousal-promoting

neurons of the basal forebrain.

• Caffeine is believed to promote wakefulness by blocking adenosine receptors.

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Circadian Rhythm

• Virtually all living organisms exhibit metabolic, physiologic, and behavioral circadian rhythms (about 24-hour)

• Sleep / Wake Cycling (amount, time)• Body temperature• Hormone secretion - ACTH, LH, FSH, melatonin, TSH,

cortisol

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“The Master Biological Clock”

• endogenous Circadian Pacemaker regulates sleep-wake and all other circadian rhythms

• resides in the suprachiasmatic nuclei (SCN) of the hypothalamus.

• SCN are bilaterally paired nuclei located slightly above the optic chiasm in the anterior hypothalamus.

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Circadian Clock Synchronizes with Environment

• Circadian clocks are normally synchronized to environmental cues by a process called entrainment.

• Light-dark cycle is the most potent entraining stimulus.

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Circadian Output• Information from the SCN is transmitted to the rest of the

body after input from the hypothalamus.

• Thus body organ response to the circadian rhythm is controlled by the SCN and modulated by the hypothalamus. • (e.g. sleep-wake cycle, core body temperature, the release of

cortisol, thyroid stimulating hormone, melatonin etc.)

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Sleep Academic Award 22

Sleep State Determination• Electrographic

• Behavioral

• Neuronal activity

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Properties of Wake, REM, NREM Behavioral

Wake NREM REM Movement frequent, infrequent, inhibited

voluntary episodic

Thought logical & logical & not illogical,remembered remembered not

rememberedunless awakened

Eyes open,moving closed, slow closed, or not moving rapidly

moving

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Properties of Wake, REM, NREM Electrographic

Wake NREM REM

EEG desynch synch desynch

EOG present slow or rapid(eye movements) absent

EMG present decreased inhibited(muscle tone)

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Clinical Evaluation of Sleep Problems

• Normal Variation

• Factors that impact on sleep

• Sleep Processes

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Factors that Impact on Sleep

DevelopmentalCircadianUltradianPrior sleep deprivation / fragmentation

NeurologicCardiopulmonaryGastrointestinal

EndocrineDermatologicUpper respiratoryAllergyDrugsPsychiatric /psychological

InfectiousPain

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Sleep History and Sleep Log

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Sleep History

•Bedtime

•Excessive daytime sleepiness

•Awakenings

•Regularity

•Snoring

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EXCESSIVE DAYTIME SLEEPINESS

Scope of the Problem

• Sleepiness is problematic when it disrupts daily living

• Problem sleepiness is estimated to affect 0.5 to 5% of the population• But 20-25% of US population does shift work

• Problem sleepiness has two primary causes:• Lifestyle factors

• Sleep disorders

Sleepiness vs. Fatigue

• Sleepiness reflects a biologic need; sleep is to sleepiness

as food is to hunger. Sleepiness refers specifically to an

increased likelihood of falling asleep. Fatigue refers to

many different conditions, some of which do not include

sleepiness. Fatigue refers specifically to increased

difficulty sustaining a high level of performance.

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Disorders of EDS

Insufficient sleep Increased drive to sleep Fragmented Sleep

•Inadequate sleep hygiene•Insufficient Sleep syndrome

•Jet Lag/sleep deprivation•Long sleeper

•Narcolepsy•Idiopathic hypersomnia

•Circadian rhythm disorders•Medical illness/Medications

•OSAS•Central sleep Apnea

•RLS•Parasomnias

Consequences of EDS• Loss of work efficiency

• Indirect health care costs• Direct costs to business

• Motor vehicle accidents

• Depression/anxiety

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Sleep Disorders - Socioeconomic Consequences

• More than 100,000 motor vehicle accidents annually are sleep-related.

• Disasters such as:• Chernobyl,• Three Mile Island,• Challenger, • Exxon Valdez were officially attributed to errors in judgement induced bysleepiness or fatigue.

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Sleepy Driving is Fatal

• The increased fatality rate is likely due to a combination of:• Reduced Vigilance• Slowed Reaction Times• Loss of Steering Control

• Sleepiness represents a significant risk to driving safety and may pose as great a risk as alcohol

• Motor vehicle accidents tend to peak during early morning and mid-afternoon hours, in accordance with times of increased sleep propensity

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Assessing Sleepiness

• Patient history

• Observer history

• Scales, tests, subjective scores

• Objective measurement

Evaluation of sleepiness• Subjective measures/ objective measures

• May be discordant

• Under reported

• Physiologic testing may not be representative of actual conditions that patients operate under

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Characteristic features of sleepiness• Physiologic Sleepiness

• Biologic drive to sleep (measured by Sleep latency)

• Manifest sleepiness• Change in individuals behavior from sleepiness

(performance, inability to stay awake, decreased performance on vigilance testing)

• Introspective sleepiness• Patients assessment of their sleep state

(questionnaires')

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Physiologic sleepiness-MSLT

• Patients have four to five 20 minute opportunities to nap during the day

• Unit of measure is minutes from lights out to sleep onset

• “Normal” is > 15 minutes• Pathologically sleepy is < 5 minutes• REM sleep during these naps is not expected

Manifest sleepiness• MWT

• 4-5 periods where patients are instructed to remain awake (after overnight PSG)

• Document response to therapy• Safe to perform their work after Tx

• Vigilance testing• Driving simulators

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Introspective sleepiness• Stanford sleepiness Scale

• Easy to use• No reference values• Not validated with physiologic sleepiness

• Epworth sleepiness Scale Score• Widely used• Mean SL on MSLT does not always correlate with score• Can not replace physiologic testing

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Clues to Sleep Deprivation:How much sleep is enough?

• “Normal” human range is 5-10 hours / night

• Alarm clock use indicates sleep curtailment

• Weekend catch-up indicates sleep curtailment

• Sleep loss proportional to number of jobs, kids

Sleep Hygiene• Regular sleep-wake schedule• Avoid caffeine• Exercise• Careful use of napping• Avoid alcohol and nicotine• Use bed only for sleep and sex• Quiet, cool (65 degrees) sleeping room

Clues to SDBWhich snorers have apnea?• Witnessed apneas

• “Heavy” snoring, impotence, sleepiness

• Hypertension

• Crowded upper airway

• Central obesity• Neck circumference > 17/16• BMI > 30

Clues to Narcolepsy:When is sleepiness genetic?

• Symptom onset in adolescence

• 0.05 % population

• HLA linked-autoimmune

• Naps are refreshing

• Family history -25 % concordance in identical twins

• Deficiency of hypocretin/orexin

• The narcolepsy “tetrad”

The Narcolepsy Tetrad

• EDS

• Cataplexy

• Hypnagogic / hypnopopnic hallucinations

• Sleep paralysis

• (Disturbed nocturnal sleep)

Diagnosing Narcolepsy

• Compatible clinical history• Rule out other causes (SDB, PLMS, sleep deprivation,

drugs)• Overnight polysomnogram is normal and includes > 6

hours sleep• Daytime MSLT shows sleepiness (mean sleep latency

< 10 minutes) plus 2 or more SOREM’s

Restless Legs vs. Periodic Limb Movements of Sleep • RLS is a collection of symptoms

• Diagnosis made by history

• 80 % of those with RLS have PLMS

• PLMS is an electromygraphic finding

• Diagnosis made in a sleep lab

• 30% of those with PLMS have RLS

Clues to a Movement Disorder:Symptoms of RLS

• Unpleasant limb sensations

• Sensations precipitated by rest and relieved by activity

• Compelling motor restlessness

• Worsening of symptoms at night

Problem Sleepiness: History

• History of apneas, snoring • Complaints of unpleasant limb sensations, worse at night, relieved by activity, associated with movement

• Medication history• Sleep diary or habits• Cataplexy, hallucinations, paralysis, family history

• Severity of sleepiness: Epworth, car wrecks

Problem Sleepiness: Examination

• BMI, blood pressure, neck circumference, airway (SDB)

• Pupils (stimulant seeker)

• Neurologic and vascular exam (RLS)

• Thyroid (hypothyroidism)

Which Sleepy Patients Go To The Sleep Lab?

• Those suspected of sleep apnea or narcolepsy

• Narcolepsy diagnosis requires PSG and MSLT; sleep apnea diagnosis requires PSG

• RLS, sleep deprivation, medication effects usually diagnosed clinically

Drug Effects

• Drugs can cause sleepiness 3 ways:• Direct pharmacologic effect• Disturbed sleep architecture• Abrupt discontinuation (withdrawal)

• Two characteristics are particularly risky:• Highly lipophilic• Affecting cholinergic, dopaminergic, or histaminergic receptors

Clues to Drug-Induced Sleepiness: Classes of Drugs• Analgesics

• Anti-asthmatic agents

• Anticonvulsants

• Antidepressants

• Antihistamines

• Antihypertensives

• Antiparkinsonian agents

• Antipsychotic agents

• Benzodiazepines

• Antiemetics

Sleep can be dangerous for patients with lung diseases

Thank You

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