Sleep Disorders

Polysomnography

comprehensive sleep study that records various physiological parameters during sleep to diagnose and monitor sleep disorders

5 Stages of Sleep

1. Wakefulness

2. NREM Stage 1

3. NREM Stage 2

4. NREM Stage 3

5. REM Sleep

Wakefulness

• Beta waves (high frequency, low amplitude)

• Alpha waves during relaxed wakefulness

• Eye movements: frequent blinking

• Muscle tone: High

• Awake and alert

NREM Stage 1 (N1)

• Low-amplitude mixed-frequency (theta waves, 4-7 Hz); ↓ alpha waves

• Eye movement: Slow rolling 

• Muscle tone: decreased

• Lightest sleep, easy to wake

NREM Stage 2 (N2)

• Sleep spindles (12-14 Hz bursts) and K-complexes (high amplitude biphasic waves)

• Eye Movement: Slow

• Muscle tone: Further decrease

• Memory consolidation, bruxism may occur

NREM Stage 3 (N3)

• Dominated by high amplitude, low frequency delta waves (0.5-2 Hz)

• Eye Movement: Minimal

• Muscle tone: Lowest tone (except REM)

• Deep, restorative sleep

REM Sleep

• Low-voltage, mixed-frequency EEG similar to wakefulness; sawtooth waves

• Eye Movement: Rapid, conjugate

• Muscle tone: Muscle atonia (near paralysis)

• Dreaming occurs, irregular breathing

Sleep Pattern

• Sleep begins with falling asleep, then progresses through increasingly deeper stages (Stage 1 → 2 → 3 → 4 of NREM sleep)

• After reaching deepest sleep, the brain returns to lighter stages before entering REM sleep

• Cycle repeats every 90-110min throughout the night

Sleep Changes Across the Night

First Half:

• Dominated by deep NREM sleep (Stages 3-4)

• Short REM periods

Second Half:

• Deep NREM sleep decreases or disappears

• REM periods become much longer, often dominating each cycle

• By morning, REM can be longer than the NREM stages

Shifting pattern supports memory processing, brain function, and emotional regulation

Insomnia Disorder

Difficulty falling asleep

Difficult staying asleep

Trouble waking early w/ an inability to fall back to sleep

Sufficient to impair their functioning

Hypersomnolence Disorder

Abnormally prolonged sleep or excessive sleepiness despite adequate or long nighttime sleep

• Primary (idiopathic hypersomnia)

• Secondary to other conditions (ex. Depression, sleep apnea, medications)

• Core Features:

  • Often sleep 10+ hours but still feel unrefreshed and tired

  • Difficulty waking (sleep drunkenness)

  • Cognitive slowing

  • Poor daytime function

Narcolepsy

• Excessive daytime sleepiness

• Irresistible sleep attacks

• Can fall asleep inappropriately

3 Types of Narcolepsy

1. Narcolepsy Type 1 (NT1)

2. Narcolepsy Type 2 (NT2)

3. Secondary Narcolepsy

Narcolepsy Type 1 (NT1)

Excessive daytime sleepiness (EDS) WITH cataplexy

• Low CSF hypocretin/orexin levels, a brain chemical regulating wakefulness

• May enter REM sleep rapidly after falling asleep

• Other symptoms:

  • Sleep paralysis

  • Hypnagogic hallucinations

  • Fragmented nighttime sleep

Narcolepsy Type 2 (NT2)

Excessive daytime sleepiness (EDS) WITHOUT catalepsy

• Normal CSF hypocretin/orexin levels

• Less severe symptoms than NT1

• Diagnosis requires exclusion of other causes of excessive sleepiness

Secondary Narcolepsy

• Rare

• Brain injury, tumors, inflammation, or lesions affecting the hypothalamus area responsible for sleep regulation

Sleep-Related Breathing Disorders Main Mechanisms

Obstructive: upper-airway collapse during sleep (most common)

Central: reduced/absent brainstem respiratory drive

Mixed: elements of both

Hypoventilation: shallow breathing w/o full pauses

Sleep-Related Breathing Disorders Types

1. Apnea

2. Hypopnea:

3. Obstructive Sleep Apnea (OSA)

4. Central Apnea

5. Hypoventilation

Apnea

breathing stops ≥10 sec

Hypopnea

Reduced airflow + arousal and/or oxygen drop

• Consequences: arousals, oxygen desaturation, sympathetic surges

Obstructive Sleep Apnea (OSA)

Risk Factors: obesity, large neck, craniofacial crowding, nasal obstruction

Central Apnea

Brain doesn't send the signal to breathe, so there's no effort from the breathing muscles, even though the airway remains open

• More about a communication failure between the brain and muscles controlling breathing, rather than a blockage

• Risk Factors: HF, stroke, opioids, high altitude, neurologic disease

Hypoventilation

Not enough air gets into the lungs, causing less oxygen and more carbon dioxide in the blood

• Physical problem: airway gets blocked or narrowed during sleep b/c throat muscles relax too much, which stops or limits airflow despite the body's effort to breathe

• Risk Factors: severe obesity, neuromuscular/chest-wall disorders, COPD/overlap

Common Presentation of Sleep-Related Breathing Disorders

Nocturnal

• Loud snoring; Witnessed apneas/gasping; Choking; Frequent awakenings; Nocturia

Daytime

• Sleepiness; Morning headaches; Dry mouth; Poor concentration; Irritability

Normal Respiration

• Regular and stable breathing pattern

• Amplitude of inhalation and exhalation remains constant over time

Cheyne-Stokes’ Respiration

Breathing gradually increases in depth, then decreases, followed by a period of apnea (temporary cessation of breathing)

Circadian Rhythm Sleep-Wake Disorders

Sleep timing problem, not sleep quality problem

• Body clock, suprachiasmatic nucleus (SCN), is out of sync w/ the desired schedule

Suprachiasmatic nucleus (SCN)

Pacemaker (~24hrs) sets rhythm (links to core body temp, melatonin)

• Location: anterior hypothalamus above the optic chiasm

• Regulates body’s 24 hour rhythms—including sleep-wake cycles, hormone release, body temperature, melatonin production (via pineal gland), and feeding—by synchronizing internal time w/ external light-dark cycle

• Sends signals to other brain regions involved in sleep regulation, like the preoptic area, which is important for non-REM sleep

• Coordinates sleep timing and quality to maintain stable breathing patterns during sleep and reduce risk of irregular breathing/apnea events

Normal Circadian Rhythm Sleep-Wake

Normally re-set daily by bright light, social cues, activity, stimulants/caffeine timing

• Desynchrony (travel, shift work, phase mismatch, intrinsic clock issues) → circadian disorders

Main Types of Circadian Rhythm Sleep-Wake Disorders

1. Delayed Sleep-Wake Phase (DSPD)

2. Advanced Sleep-Wake Phase (ASPD)

3. Irregular Sleep-Wake Rhythm

4. Non-24-Hour Sleep-Wake Rhythm (Non-24)

5. Shift Work Disorder

6. Jet Lag Disorder

Delayed Sleep-Wake Phase (DSPD)

• “night owl”

• Can’t fall asleep until late

• Struggles w/ early mornings

• Normal sleep if allowed late schedule

Advanced Sleep-Wake Phase (ASPD)

• “early bird”

• Very early sleep onset and early awakening

• Common in older adults

Irregular Sleep-Wake Rhythm

Fragmented, multiple short sleep bouts over 24 hrs

Often neurodegenerative or developmental contexts

Non-24-Hour Sleep-Wake Rhythm (Non-24)

• Sleep time drifts later each day (free-runs) b/c w/o proper synchronization w/ light or environmental signals, their "day" keeps getting pushed back

  • Sleep-wake cycle >24hrs

• Classically seen in totally blind /c their brains cannot receive light input to reset the circadian clock via the suprachiasmatic nucleus (SCN)

• Can occur in sighted individuals if their circadian system or its neural inputs are dysfunctional

• Ex. 25 hours 46 minutes cycle → shifts ~1 hour later each day

Shift Work Disorder

Insomnia or sleepiness tied to night/rotating shifts

Jet Lag Disorder

Transient insomnia/sleepiness after rapid time-zone travel

Parasomnia

Abnormal movements, behaviors, emotions, perceptions, or dreams that happen during sleep, while falling asleep, or at transitions b/w wakefulness and sleep stages

Impact of Parasomnia

• Disrupt person's own sleep and sometimes others

• Often has little or no memory of the episode on waking

• More common in children but can affect adults

Types of Parasomnia

• Non-REM (NREM) parasomnias

• REM parasomnias

• Other: exploding head syndrome, sleep-related hallucinations, bedwetting

Key Features of NREM parasomnias

• Timing: Occurs during deep sleep (mostly first half of night)

• Partial awakening w/ absent or little memory of events

• Common in children but also affect adults

• Triggered by stress, sleep deprivation, or noise

Ex. confusional arousal, sleepwalking (somnambulism), sleep terrors (night terrors), sexsomnia (sleep-related sexual abnormal behavior), sleep talking (can occur in any sleep stage)

NREM Parasomnias Treatment

• Safety measures

• Good sleep hygiene

• Sometimes medications (benzodiazepines or melatonin)

Sleep Terror (Night Terrors)

State: arise from N3 (slow-wave) sleep

Timing: first third of the night

Presentation:

• Sudden piercing scream/cry

• Intense fear/panic

• Autonomic surge (↑HR, ↑BP sweating)

• Incoherent vocalizations

Responsiveness/Recall:

• Unresponsive or hard to console

• If awakened → confused/disorientated w/ amnesia for the event

Severity: infrequent (<monthly) to near-nightly w/ injury (severe)

Triggers/Risk Factors of Sleep Terror (Night Terror)

Sleep deprivation

Fever

CNS-depressant withdrawal

Can be potentiated by OSA (Obstructive Sleep Apnea) and medications

Familial tendency

Epidemiology of Sleep Terror (Night Terror)

Common in children (usually benign)

In adults, more often associated w/ trauma/psychiatric comorbidity

Confusional Arousals

Episodes of partial awakening from deep (NREM) sleep, during which the person is confused and disoriented

Timing:

• First third of the night

• Lasts a few minutes (sometimes longer)

Symptoms:

• Sitting up in bed, mumbling, or staring blankly

• Difficult awakening fully during episode

• Little or no memory of event upon full awakening

Features:

• Person usually stays in bed (does not walk)

• No prominent fear or agitation

• Typically benign and self-limited

Triggers/Risk Factors of Confusional Arousals

Sleep deprivation, illness, irregular sleep, stress

Epidemiology of Confusional Arousals

Common in children, but can affect adults

Management of Confusional Arousals

• Prioritize safety (avoid injury)

• Good sleep hygiene

• Regular sleep schedule

• Medical evaluation if frequent or risky episodes

Sleep-Related Eating Disorder

Recurrent episodes of involuntary eating and drinking during sleep

Timing: non-REM sleep

Symptoms:

• Eating unusual or high-calorie foods unconsciously

• Preparing and consuming food while partially asleep

• Little to no memory of episodes upon waking

• Risk of injury from handling sharp or hot objects

• Nighttime eating disrupts sleep quality

Associated Factors:

• Coexists with other sleep disorders (ex. OSA or restless legs syndrome)

Trigger/Risk Factors of Sleep-Related Eating Disorder

Triggered by medications (ex. zolpidem)

Weight gain and metabolic issues

Psychological distress

Management of Sleep-Related Eating Disorder

Treat underlying sleep disorders

Medication review and adjustments

Safety measures in sleep environment

Behavioral therapies

Key Features of REM parasomnias

• Muscle atonia (normal paralysis during REM) is lost, allowing dream enactment

• Associated w/ vivid dreams and often full recall upon awakening

• Common in older males

• Linked to neurological disease

Ex. REM sleep behavior disorder, recurrent isolated sleep paralysis (RISP), nightmare disorder

Treatment of REM parasomnias

• Medication (clonazepam, melatonin)

• Safe sleep environment

REM Sleep Behavior Disorder

Loss of normal REM atonia → patient acts out dreams

Timing:

• REM-predominant → often last third of the night 

Typical behaviors:

• Punching, kicking, leaping, diving, grabbing

• Movements match dream content

Dream state:

• Person is immersed in the dream (not aware of the room)

Injury risk:

• Common and can be severe (cut, fractures) to patient/partner

Triggers/Associations of REM Sleep Behavior Disorder

Can be drug-induced or worsened (ex. certain antidepressants)

Associated w/ neurologic disease (ex. Parkinson’s, Lewy body dementia)

Nightmare Disorder

Recurrent, distressing dreams that are vivid and frightening, lead to awakening, and cause daytime distress/impairment

Timing: REM sleep → often second half of the night

• Evolves from long, elaborate dreams

Recall:

• On awakening, clear recall of the dream (vs. sleep terrors w/ amnesia/confusion)

Autonomic signs:

• Sympathetic activation (tachycardia, sweating) that resolves after full awakening

Impact: Can drive insomnia (fear of sleeping)

Epidemiology of Nightmare Disorder

Common in children (3-6 year olds); Less common in adults

May be recurrent

Triggers/Associations of Nightmare Disorder

• PTSD/trauma (dreams may replay events, immediately or delayed; can persist for years)

• Medications: L-DOPA, β-blockers

• Rebound: After stopping REM-suppressants (ex. alcohol, some antidepressants)

• Substances: alcohol/drug use; withdrawal

• Stress, sleep deprivation, irregular schedule

Recurrent Isolated Sleep Paralysis (RISP)

Brief episodes of inability to move or speak that occurs right as you’re falling asleep or walking up

Core Features of Recurrent Isolated Sleep Paralysis (RISP)

• Consciousness is intact

• Breathing continues

• Episodes end spontaneously within seconds to a few minutes

• “Recurrent”: happens repeatedly, causes distress or functional impairment

• “Isolated”: not d/t narcolepsy, medication, or another sleep/medical disorder

What does Recurrent Isolated Sleep Paralysis (RISP) feel like?

Awake but paralyzed

• Often w/:

  • Chest pressure

  • “Presence in the room,”

  • Vivid hallucinations (visual/auditory/tactile)

  • Anxiety/fear, sometimes panic

Triggers of Recurrent Isolated Sleep Paralysis (RISP)

Sleep deprivation

Irregular schedule

Sleeping supine

Jet lag

Stress

Alcohol

Some antidepressants or withdrawal

Comorbid insomnia or OSA

Sleep-Related Hallucinations

Vivid, often visual images at sleep onset (hypnagogic) or on awakening (hypnopompic)

Features:

• Immobilized, static images that can last minutes

• May feel “real”

• Often noticed when a light is turned on

• Can be frightening

Association:

• Common in narcolepsy

• Can occur in healthy people.

Recall/Context:

• May be hard to distinguish from dreams

• Complex forms can occur after abrupt awakening w/o dream recall

Sleep Enuresis

Involuntary urination during sleep

Types:

• Primary: never sustained dryness since infancy (most common)

• Secondary: relapse after ≥6 months dry

Natural history: Often resolves spontaneously by ~age 6

Risk Factor: Family history (strong; likely genetic component)

Associations (secondary):

• New sibling/stress

• Sleep deprivation

• Nocturnal seizures

• UTIs

• Constipation

• Anatomic/urologic issues

• Diabetes

• OSA (children & adults)

Restless Legs Syndrome

Uncomfortable limb sensations (usually legs; “creepy-crawly,” ants on skin) + irresistible urge to move

Pattern:

• Worse at rest/evening/night

• Relieved by movement (walking, stretching)

• Can cause sleep-onset insomnia

URGE mnemonic (Diagnosis)

• Urge to move the legs

• Rest/triggers worsen it

• Gets better with movement

• Evening/night worse

Sleep-Related Bruxism

Involuntary teeth grinding/clenching during sleep → tooth wear, jaw/tooth pain, headaches, bed-partner noise

When it happens:

• Any stage; Often at sleep onset, N2, and REM

• REM-related bruxism may cause more dental wear

Triggers/Associations:

• Stress

• Sleep-related breathing disorders (OSA)

• Psychostimulants (amphetamine, cocaine)

• Alcohol

• Some SSRIs

Not caused by: dental malocclusion (no consistent link)

Severity grading: by sleep disruption, pain, dental damage (nightly > weekly > monthly)

Good Sleep Hygiene

• Maintain regular hours of bedtime and arising

• If you are hungry, have a light snack before bedtime

• Maintain a regular exercise schedule

• Give yourself approximately an hour to wind down before going to bed

• If you are preoccupied or worried about something at bedtime, write it down and deal with it in the morning

• Keep the bedroom cool

• Keep the bedroom dark

• Keep the bedroom quiet

Bad Sleep Hygiene

• Watch the clock so you know how bad your insomnia actually is

• Exercise right before going to bed in order wear yourself out

• Watch television in bed when you cannot sleep

• Eat a heavy meal before bedtime to help you sleep

• Drink coffee in the afternoon and evening

• Take naps

• If you cannot sleep, smoke a cigarette

• Use alcohol to help in going to sleep

• Read in bed when you cannot sleep

• Eat in bed

• Exercise in bed

• Talk on the phone in bed