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The Science of Sleep

The Science of Sleep. 2 Phases: REM and Non-REM Sleep. Physiology of Normal Sleep. 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. Stage One.

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The Science of Sleep

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  1. The Science of Sleep

  2. 2 Phases: REM and Non-REM Sleep Physiology of Normal Sleep

  3. 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

  4. Stage One • Brief transition between wakefulness and sleep (accounts for only 5% of sleep time)

  5. Stage Two • Light sleep • Accounts for 50% of total sleep time • ElectroEncephaloGram (EEG) shows some characteristic findings…

  6. EEG in Stage 2

  7. 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

  8. 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

  9. 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

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

  11. 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

  12. 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

  13. 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)

  14. 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

  15. Sleep Disorders

  16. 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

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

  18. 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

  19. 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

  20. Consequences of Insomnia • Depression • Irritability • Decreased cognitive functioning • Decreased productivity • Injuries and accidents

  21. 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)

  22. Narcolepsy Tetrad • Classic tetrad of associated findings: • 1. Sleep attacks • 3. Sleep paralysis • 4. Sleep hallucinations

  23. 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

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

  25. 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)

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

  27. Sleep Apnea: Two Types • Obstructive Sleep Apnea: most common • Central Sleep Apnea

  28. Obstructive Sleep Apnea • Classic- obese, middle-aged male with thick neck or enlarged tonsils • Apneas- brief gasps…silence, followed by loud “resuscitative” snores, and sometimes body movements (restless) • Usually unaware of snoring, arousals…but sleep partner is aware

  29. 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

  30. Sleep Apnea: Consequences • Depression • Anxiety • Morning headaches • Cognitive dysfunction • Hypertension

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

  32. RLS Causes • Peripheral neuropathies • Peripheral vascular disease • Medication side effects • Anemia • Pregnancy • Renal failure

  33. Circadian Rhythm Disorders • Delayed Sleep Phase Syndrome • Jet Lag • Accelerated Sleep Phase Syndrome • Shift Work Sleep Disorder

  34. Psychiatric Causes of Insomnia • Depression • Anxiety • Psychosis • Substance intoxication/withdrawal

  35. The End

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