Sleep Disorders Study Notes

Sleep Disorders Overview

  • Introduction to the concept of sleep disorders, sleep cycles, and sleep phases.
  • High prevalence of undiagnosed sleep disorders: 80% of individuals remain undiagnosed.
  • Economic impact of sleep disorders in the US: $400,000,000,000 due to accidents, injuries, and personal problems.
  • Importance of sleep: even minimal sleep can lead to significant impairment; compares sleep deprivation to smoking and driving under the influence.

Importance of Sleep

  • Physiological consequences of sleep deprivation include:
    • Disruption of immunity
    • Cardiovascular effects
    • Low-grade immune inflammatory state with cytokine production
    • Hypertension issues
    • Disrupted glucose metabolism and insulin sensitivity
    • Increased rates of diabetes
    • Impaired attention, executive functioning, learning, reaction times, and emotional regulation
    • Increased risk for neurological diseases due to lack of sleep cleaning out the brain

Insomnia

  • Definition: Inability to fall asleep or stay asleep.
  • Prevalence: Occurs in 30-35% of adults, including children.
  • Comorbid conditions include:
    • Stress
    • Drug and alcohol use
    • Chronic pain
    • Depression
    • Aging (especially fragmented sleep in elders)
    • Chronic diseases (lung and cardiac conditions, dementia, menopause, and reflux)

Physiological Processes in Insomnia

  • Hyperarousal of the prefrontal cortex.
  • Reduced cortical GABA levels; GABA promotes sleep by activating the Ventrolateral Preoptic (VLPO) area.
  • Increased arousals during REM sleep and dysregulation of sleep-wake cycles.
  • Physiological characteristics in insomnia:
    • Reduced hippocampal volume
    • Increased amygdala activity
    • Reduced frontal volume and task-related activity
    • Increased anterior cingulate cortical volume
    • Increased thalamic activation during sleep, which disrupts calmness needed for sleep.

Genetic and Epigenetic Factors in Insomnia

  • Familial components: Insomnia can run in families, seen in twin studies.
  • Genetic vulnerability: 30-50% of first-degree relatives also experience insomnia.
  • Epigenetic factors may influence stress-induced sleep disturbances.

Treatments for Insomnia

  • Pharmacological options often target the GABA system to inhibit arousal and promote sleep.
  • Importance of sleep hygiene in long-term management of insomnia.

Obstructive Sleep Apnea Syndrome (OSAS)

  • Definition: Disordered breathing during sleep due to airway collapse.
  • Prevalence:
    • 1-5% in children
    • 2-15% in middle-aged adults
    • Over 20% in elderly (1 out of 5)
  • Gender differences: More prevalent in men due to physical structure.
  • Risk factors include obesity, which increases physical pressure leading to airway collapse during sleep.
  • Consequences of airway collapse:
    • Increased CO2 and decreased oxygen levels lead to arousal.
    • Most severe during REM sleep due to muscle relaxation.

Physiological Changes in OSAS

  • Hypoxia stimulates receptors in the carotid body, increasing sympathetic outflow.
  • Increased renin release from kidneys leading to various cardiovascular outcomes:
    • Endothelial dysfunction
    • Vascular resistance and stiffness
    • Increased risk of atherosclerosis

Narcolepsy

  • Definition: Rare disorder characterized by hypersomnolence and difficulty sustaining wakefulness.
  • Prevalence: Approximately 25-50 per 100,000 people.
  • Symptoms include:
    • Daytime sleepiness
    • Cataplexy (sudden muscle weakness)
    • Hypnagogic hallucinations
    • Sleep paralysis
  • Pathophysiology involves:
    • Autoimmune destruction of orexin-producing neurons that regulate wakefulness.
    • Genetic susceptibility involving certain human leukocyte antigens.

Circadian Rhythm Disorders

  • Definition: Disorders arising from disruptions in the body's internal biological clock (circadian rhythm).
  • Common in shift workers, blind individuals, and those with delayed sleep-wake disorder.
  • Physiological processes leading to symptoms of disrupted sleep patterns, increased risk of poor alertness, performance issues, and health problems, including cancer.

Parasomnias

  • Non-REM parasomnias involve behaviors during partial arousal.
  • Common conditions include:
    • Sleep terrors in pediatric populations, characterized by inconsolable agitation during partial awakenings.
    • Sleepwalking and confusional arousal
  • Implications for treatment often include reassurance for parents, recognizing that these phenomena usually resolve with age.

Restless Leg Syndrome (RLS)

  • Definition: Condition characterized by an irresistible urge to move the legs, interrupting sleep.
  • Prevalence: Affects approximately 4-10% of the population, more common in women.
  • Risk factors: Iron deficiency, family history, pregnancy, and certain medications.

Theoretical Mechanisms of RLS

  • Potential links to iron transport across the blood-brain barrier affecting dopamine production (though not all cases are related to iron deficiency).
  • Dopaminergic dysfunction is thought to play a role, alongside potential adenosine and GABA neurotransmitter disturbances.

Evaluation of Sleep Disorders

  • Tools for assessment include:
    • STOP-BANG questionnaire for assessing sleep apnea risk.
    • Nocturnal oximetry to monitor oxygen saturation.
    • Polysomnography to analyze sleep architecture, heart rhythm, and other parameters.
    • Multiple Sleep Latency Test for diagnosing narcolepsy.
    • Sleep history and diary logging for insomnia and related conditions.

Role of Sleep Hygiene

  • Importance of sleep hygiene in managing insomnia and circadian rhythm disorders:
    • Consistent sleep schedules help anchor circadian rhythms.
    • Light exposure management to align with the body's sleep-wake cycle.
    • Maintaining a dark, cool environment to facilitate sleep.
    • Limiting screen time and bright light exposure before bed to enhance melatonin secretion.
  • Establishing calming bedtime routines to support relaxation, especially for children.