Sleep Wake Disorders

Introduction to Sleep Disorders for MCCQE1

Sleep-wake disorders are a high-yield topic for the MCCQE1, reflecting their high prevalence in the Canadian population. Approximately 25% of Canadians report dissatisfaction with their sleep. As a future Canadian physician, you must be proficient in diagnosing, managing, and recognizing the safety implications of these disorders, particularly regarding fitness to drive.

This guide covers the pathophysiology, clinical presentation, and management of major sleep disorders, aligned with the CanMEDS framework (specifically Medical Expert and Health Advocate roles) and DSM-5-TR/ICSD-3 criteria.

Classification of Sleep Disorders

The International Classification of Sleep Disorders (ICSD-3) groups disorders into major categories. Understanding these distinctions is crucial for the differential diagnosis on the MCCQE1.

Clinical Approach to Sleep Complaints

A structured approach is vital for the Medical Council of Canada Qualifying Examination Part I.

High-Yield Mnemonic: BEARS

Use this for pediatric and adult history taking.

Major Sleep Disorders

1. Insomnia Disorder

Defined as dissatisfaction with sleep quantity or quality associated with one or more symptoms (difficulty initiating, maintaining, or early awakening) causing significant distress/impairment, occurring at least 3 nights/week for at least 3 months.

• Epidemiology: Most common sleep disorder in Canada.
• Management:
  1. Sleep Hygiene: First-line education.
  2. CBT-i (Cognitive Behavioural Therapy for Insomnia): The gold standard first-line treatment in Canadian guidelines.
  3. Pharmacotherapy: Short-term use only.
     • Z-drugs (Zopiclone, Zolpidem).
     • Benzodiazepines (Temazepam) – Avoid in elderly (Beers Criteria).
     • Orexin antagonists (Lemborexant) – Newer, approved in Canada.

2. Obstructive Sleep Apnea (OSA)

Recurrent collapse of the upper airway during sleep, leading to hypoxia and sleep fragmentation.

• Risk Factors: Obesity, male gender, age, alcohol use, retrognathia.
• Screening Tool: STOP-BANG questionnaire.
• Diagnosis:
  • Polysomnography (Level 1 or 3 study): Gold standard.
  • Diagnostic Criteria: Apnea-Hypopnea Index (AHI) > 5 events/hour with symptoms, or AHI > 15 without symptoms.
• Complications: Hypertension (resistant), Atrial Fibrillation, Stroke, Pulmonary Hypertension.
• Treatment:
  • Lifestyle: Weight loss, avoid alcohol/sedatives, positional therapy.
  • CPAP (Continuous Positive Airway Pressure): Treatment of choice for moderate-severe OSA.
  • Oral Appliances: Mandibular advancement devices for mild-moderate OSA.

3. Narcolepsy

A central disorder of hypersomnolence caused by the loss of orexin (hypocretin) neurons.

• Tetrad of Symptoms:
  1. Excessive Daytime Sleepiness (EDS): Universal symptom.
  2. Cataplexy: Sudden loss of muscle tone triggered by strong emotion (laughter/anger). Pathognomonic for Type 1.
  3. Sleep Paralysis: Upon falling asleep or waking.
  4. Hypnagogic/Hypnopompic Hallucinations: Vivid dreams at sleep onset/offset.
• Diagnosis:
  • Polysomnography (rule out other causes) followed by Multiple Sleep Latency Test (MSLT) showing mean sleep latency < 8 min and ≥ 2 Sleep-Onset REM periods (SOREMPs).
  • CSF Hypocretin-1 levels (low/absent in Type 1).
• Treatment:
  • EDS: Modafinil, Methylphenidate, Solriamfetol.
  • Cataplexy: SSRIs/SNRIs (Venlafaxine), Sodium Oxybate.

4. Restless Legs Syndrome (Willis-Ekbom Disease)

Urge to move legs, usually accompanied by uncomfortable sensations.

• URGE Criteria:
  • Urge to move.
  • Rest worsens symptoms.
  • Getting up/moving improves symptoms.
  • Evening/night worsening.
• Etiology: Primary (idiopathic) or Secondary (Iron deficiency, pregnancy, renal failure).
• Workup: Check Ferritin. Iron deficiency is a key reversible cause. Target Ferritin > 50-75 µg/L.
• Treatment: Iron replacement, Alpha-2-delta ligands (Gabapentin, Pregabalin), Dopamine agonists (Pramipexole – watch for augmentation).

5. Parasomnias

Disorders characterized by abnormal behavioral, experiential, or physiological events occurring in association with sleep, specific sleep stages, or sleep-wake transitions.

Canadian Guidelines & Legislation

Fitness to Drive (CMA Driver’s Guide)

This is a critical area for MCCQE1 scenarios involving ethics and legalities.

• Reporting: Know the legislation in your province (Mandatory vs. Discretionary). In exams, generally assume a duty to report if public safety is at risk and the patient is non-compliant.
• OSA: Patients with untreated OSA causing EDS should not drive. Can return to driving once treatment (CPAP) is effective and adherence is confirmed.
• Narcolepsy: Must be symptom-free on medication to drive.

Choosing Wisely Canada

• Don’t order polysomnography for chronic insomnia unless there are symptoms suggestive of sleep apnea or parasomnia.
• Don’t prescribe antipsychotics as a first-line intervention for insomnia in adults.

Key Points to Remember for MCCQE1

• OSA: The most common cause of secondary hypertension. Always screen hypertensive patients for snoring/apnea.
• Insomnia: CBT-i is the first-line treatment, not pills.
• RBD: If an elderly male presents with acting out dreams, think Parkinson’s or Lewy Body Dementia.
• Narcolepsy: Look for “knees buckling with laughter” (Cataplexy).
• Pediatrics: Adenotonsillar hypertrophy is the most common cause of OSA in children. Treatment is adenotonsillectomy.
• Safety: Always address driving safety in the management plan for hypersomnolence.

Sample Question

Clinical Scenario

A 52-year-old male presents to his family physician with a 2-year history of loud snoring and excessive daytime fatigue. His wife reports that he “stops breathing” frequently during the night. He has a history of hypertension and type 2 diabetes. His BMI is 34 kg/m². Physical examination reveals a crowded oropharynx (Mallampati Class IV) and a neck circumference of 44 cm. He works as a long-haul truck driver.

Which of the following is the most appropriate next step in management?

Options

• A. Prescribe zopiclone 7.5 mg at bedtime
• B. Recommend weight loss and follow up in 6 months
• C. Arrange for urgent polysomnography and advise him not to drive
• D. Order thyroid function tests (TSH)
• E. Refer for uvulopalatopharyngoplasty (UPPP)

Explanation

The correct answer is:

• C. Arrange for urgent polysomnography and advise him not to drive

Detailed Explanation: This patient has a high pre-test probability for Obstructive Sleep Apnea (OSA) based on his symptoms (snoring, witnessed apneas, fatigue), comorbidities (HTN, DM2), and physical exam findings (Obesity, Mallampati IV, large neck).

• Choice C is correct: The gold standard for diagnosis is polysomnography. Crucially, because he is a commercial driver (high risk) with symptoms of sleep apnea (excessive fatigue), Canadian guidelines (CMA Driver’s Guide) mandate that he should be advised not to drive until his condition is investigated and treated. Public safety is the priority.
• Choice A is incorrect: Sedatives like zopiclone can worsen OSA by relaxing upper airway muscles and reducing respiratory drive.
• Choice B is incorrect: While weight loss is part of long-term management, delaying diagnosis in a symptomatic commercial driver is negligent.
• Choice D is incorrect: While hypothyroidism can cause fatigue and weight gain, the clinical picture strongly points to OSA. TSH might be part of a workup, but it is not the most appropriate next step compared to addressing the immediate safety risk and primary differential.
• Choice E is incorrect: Surgery is generally a second-line option or reserved for specific anatomical abnormalities. CPAP is the first-line treatment for moderate-severe OSA, which must be diagnosed first.

References

1. Medical Council of Canada. MCC Objectives for the Qualifying Examination. Available at mcc.ca .
2. Canadian Medical Association. CMA Driver’s Guide: Determining Medical Fitness to Operate Motor Vehicles, 9th Edition.
3. Choosing Wisely Canada. Insomnia and Anxiety in Older Adults. Available at choosingwiselycanada.org .
4. American Academy of Sleep Medicine. International Classification of Sleep Disorders, 3rd ed. (ICSD-3).
5. Public Health Agency of Canada. Sleep Apnea: What is it? Available at canada.ca .