The Science of Sleep

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The Science of Sleep
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Physiology of Normal Sleep

• 2 Phases REM and Non-REM Sleep

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Non-REM Sleep

• 4 stages of progressively deeper sleep
• Normal muscle tone
• Associated with increased 5HT (serotonin)
• Decreased autonomic activity
• Lower BP, Pulse, respirations slow

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Stage One

• Brief transition between wakefulness and sleep
  (accounts for only 5 of sleep time)

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Stage Two

• Light sleep
• Accounts for 50 of total sleep time
• ElectroEncephaloGram (EEG) shows some
  characteristic findings

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EEG in Stage 2
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Stages 3,4

• Most restful, restorative stages of sleep
• Aka Delta wave sleep/ slow wave sleep
• Greatest proportion is in the first 1/3 to 1/2 of
  night

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NREM Sleep Theories of its purpose

• The decrease in metabolic demand on the brain
  during NREM allows glycogen stores to replenish
• Allows for consolidation of memories and learning

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REM (dreamland)

• 10-20 min. cycles consisting of
• Rapid Eye Movements
• ElectroEncepahaloGram shows fast activity very
  similar to wakeful EEG pattern
• Suppression of peripheral muscle tone
• Often increased autonomic tone- ie, increased
  blood pressure, resp, heart rate

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REM (dreamland)

• Where dreaming occurs
• REM is marked by increased brainwave activity
• Thus REM-supression seen with anti-cholinergic
  drugs (ex. some antidepressants)

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Normal Sleep Pattern

• Sleep cycles between NREM and REM approx. 4-5
  times/night
• Cycles last approx. 90min
• REM duration and frequency increase thru night
• Proportion of slow wave sleep (stages 3,4)
  decreases thru night

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Normal Sleep Parameters

• Sleep Onset Latency- the time it takes one to
  fall asleep, averages 10-20min
• REM Latency- time between sleep onset and the
  first REM period, averages 90-120min

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Normal Sleep Distribution

• REM sleep accounts for approximately 25 of total
  sleep time
• Non-REM sleep accounts for 75 of sleep time,
  with 25 of that spent in Stages 3,4 (most
  restful portion)

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Age-Related Changes

• Decreases in dreaming, total sleep time, REM, and
  slow-wave (deep sleep)
• Increases in early morning awakening,
  fragmentation, daytime napping, and phase
  advancement-
• Ie, earlier to bed, and awaken earlier

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Sleep Disorders
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Sleep Disorders- 2 Divisions

• Dyssomnias- disorders of quality, timing, or
  amount of sleep (quantity)
• Parasomnias- abnormal behaviors associated with
  sleep or sleep-wake transition, that often
  produce arousals

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Dyssomnias

• Primary Insomnia
• Narcolepsy
• Sleep Apnea
• Circadian Rhythm Sleep Disorder (jet lag, et al.)
• Restless Legs Syndrome (RLS)
• Medical/Substance related insomnia

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Primary Insomnia

• Primary, meaning no underlying medical cause
• Onset often with stressor or disruption to sleep
  schedule or environment
• Results from poor sleep hygiene, along with
  classical conditioning-
• Faulty learning/association of sleep environment
  with state of arousal

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INSOMNIA- an epidemic?

• Definition Subjective experience of poor sleep
  quality or quantity that adversely affects daily
  functioning
• Extremely common complaint in general practice
• 30-40 adults have occasional poor sleep
• 15-20 adults have chronic insomnia

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Consequences of Insomnia

• Depression
• Irritability
• Decreased cognitive functioning
• Decreased productivity
• Injuries and accidents

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Narcolepsy

• A dyssomnia characterized by poor sleep quality
  (restless, fragmented) and dysfunction in the
  transitions between sleep and wakefulness
• Presents with Excessive Daytime Sedation (EDS)

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Narcolepsy Tetrad

• Classic tetrad of associated findings
• 1. Sleep attacks
• 3. Sleep paralysis
• 4. Sleep hallucinations

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Cataplexy

• Sudden loss of muscle tone (rarely full body
  paralysis) caused by intrusion of REM activity
  into daytime wakefulness
• Triggered by heightened emotion
• Average duration 30 seconds
• No loss of consciousness

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Sleep Paralysis

• Brief paralysis upon waking
• Remain alert with full eye movements Can occur in
  the absence of Narcolepsy (ie, normal variant)

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Sleep Hallucinations

• Hypnogogic hallucinations- occur during
  transition into sleep
• Hynopompic hallucinations- occur upon awakening
  from sleep
• Can occur in the absence of Narcolepsy (ie,
  normal variant)

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Sleep Apnea

• Dyssomnia characterized by poor sleep quality due
  to frequent awakenings (apneas)
• Apneas last sec-minutes
• Presents with excessive daytime sedation- EDS

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Sleep Apnea Two Types

• Obstructive Sleep Apnea most common
• Central Sleep Apnea

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Obstructive Sleep Apnea

• Classic- obese, middle-aged male with thick neck
  or enlarged tonsils
• Apneas- brief gaspssilence, followed by loud
  resuscitative snores, and sometimes body
  movements (restless)
• Usually unaware of snoring, arousalsbut sleep
  partner is aware

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Central Sleep Apnea

• Apneas- episodic cessation of central ventilation
  drive
• Thus snoring is less common
• More in elderly, with underlying CNS lesions- ex.
  tumor, stroke

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Sleep Apnea Consequences

• Depression
• Anxiety
• Morning headaches
• Cognitive dysfunction
• Hypertension

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Restless Legs Syndrome

• Paresthesias and/or dysesthesias in the legs,
  relieved by movements
• Usually occur in transition from wakefulness to
  sleep

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RLS Causes

• Peripheral neuropathies
• Peripheral vascular disease
• Medication side effects
• Anemia
• Pregnancy
• Renal failure

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Circadian Rhythm Disorders

• Delayed Sleep Phase Syndrome
• Jet Lag
• Accelerated Sleep Phase Syndrome
• Shift Work Sleep Disorder

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Psychiatric Causes of Insomnia

• Depression
• Anxiety
• Psychosis
• Substance intoxication/withdrawal

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The End