the science of sleep
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
2 Phases: REM and Non-REM 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
Brief transition between wakefulness and sleep (accounts for only 5% of sleep time)
Stage Two
Light sleep Accounts for 50% of total sleep time ElectroEncephaloGram (EEG) shows
some characteristic findings…
EEG in Stage 2
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
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
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
REM (dreamland)
Where dreaming occurs REM is marked by increased
brainwave activity Thus REM-supression seen with anti-
cholinergic drugs (ex. some antidepressants)
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
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
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)
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
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
Dyssomnias
Primary Insomnia Narcolepsy Sleep Apnea Circadian Rhythm Sleep Disorder (jet
lag, et al.) Restless Legs Syndrome (RLS) Medical/Substance related insomnia
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
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
Consequences of Insomnia
Depression Irritability Decreased cognitive functioning Decreased productivity Injuries and accidents
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)
Narcolepsy Tetrad
Classic tetrad of associated findings: 1. Sleep attacks 3. Sleep paralysis 4. Sleep hallucinations
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
Sleep Paralysis
Brief paralysis upon waking Remain alert with full eye
movements Can occur in the absence of Narcolepsy (ie, normal variant)
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)
Sleep Apnea
Dyssomnia characterized by poor sleep quality due to frequent awakenings (apneas)
Apneas last sec-minutes Presents with excessive daytime
sedation- EDS
Sleep Apnea: Two Types
Obstructive Sleep Apnea: most common
Central Sleep Apnea
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
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
Sleep Apnea: Consequences Depression Anxiety Morning headaches Cognitive dysfunction Hypertension
Restless Legs Syndrome
Paresthesias and/or dysesthesias in the legs, relieved by movements
Usually occur in transition from wakefulness to sleep
RLS Causes
Peripheral neuropathies Peripheral vascular disease Medication side effects Anemia Pregnancy Renal failure
Circadian Rhythm Disorders
Delayed Sleep Phase Syndrome
Jet Lag Accelerated Sleep
Phase Syndrome Shift Work Sleep
Disorder
Psychiatric Causes of Insomnia Depression Anxiety Psychosis Substance intoxication/withdrawal