A 57-year-old man comes to the physician because of a 3-month history of fatigue, difficulty swallowing, and weight loss. He has smoked 1 pack of cigarettes daily for 30 years. He is 173 cm (5 ft 8 in) tall, and weighs 54 kg (120 lb); BMI is 18 kg/m2. Upper gastrointestinal endoscopy shows an exophytic tumor at the gastroesophageal junction. The patient is diagnosed with advanced esophageal adenocarcinoma. Palliative treatment is begun. Two months later, he complains of difficulty sleeping. His husband says that the patient does not get out of bed most days and has lost interest in seeing his friends. Mental status examination shows a blunted affect, slowed speech, and poor concentration. This patient is at increased risk of developing which of the following findings on polysomnography?

Increased periodic sharp-wave discharge

Increased slow-wave sleep-cycle duration

Increased spike-and-wave discharge

A 59-year-old man presents to his primary care provider with the complaint of daytime fatigue. He often has a headache that is worse in the morning and feels tired when he awakes. He perpetually feels fatigued even when he sleeps in. The patient lives alone, drinks 2-3 beers daily, drinks coffee regularly, and has a 10 pack-year smoking history. His temperature is 99.0°F (37.2°C), blood pressure is 180/110 mm Hg, pulse is 80/min, respirations are 13/min, and oxygen saturation is 98% on room air. Physical exam is notable for a BMI of 39 kg/m^2. The rest of the patient's pulmonary and neurological exams are unremarkable. Which of the following is the best next step in management?

Alcohol avoidance in the evening

A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

"Can you tell me more about the symptoms you have been experiencing?"

"Does the diarrhea typically precede the constipation, or vice-versa?"

"Is the diarrhea foul-smelling?"

"Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"

"Are the symptoms worse in the morning or at night?"

A first time mother of a healthy, full term, newborn girl is anxious about sudden infant death syndrome. Which of the following pieces of advice can reduce the risk of SIDS?

Sleep supine in a crib without bumpers, use a pacifier after 1 month of age, and avoid smoking

Sleep supine in a crib with bumpers, head propped up on a pillow, and wrapped in a warm blanket

Sleep supine in a crib with bumpers, head propped up on a pillow, and wrapped in an infant sleeper

Sleep supine in the parent's bed and use a pacifier after 1 month of age

Sleep supine in a crib without bumpers, use a pacifier after 1 month of age, and use a home apnea monitor

Circadian rhythm sleep-wake disorders for USMLE Step 3: High-Yield Psychiatry Lessons

Circadian Essentials - The Body's Clockwork

Circadian rhythm pathway, melatonin, and sleep disorders

Master Clock: The suprachiasmatic nucleus (SCN) in the hypothalamus orchestrates the body's ~24-hour cycle.
Primary Zeitgeber ("Time Giver"): Light is the most powerful external cue.
- Specialized retinal ganglion cells perceive light, signaling the SCN.
Hormonal Control:
- Melatonin: Produced by the pineal gland. Its secretion ↑ in darkness (promoting sleep) and ↓ with light exposure.
- Cortisol: An adrenal steroid that peaks in the early morning, promoting alertness.

⭐ The SCN is the master clock, located in the anterior hypothalamus, receiving direct input from the retina.

Disorder Types - Out-of-Sync Sleepers

Disorder	Core Feature	Common Population / Mnemonic
Delayed Sleep-Wake Phase	Sleep-wake times are later than desired/conventional. Can't fall asleep until late (e.g., 2-6 AM) and difficulty waking.	📌 'Night Owls'; adolescents.
Advanced Sleep-Wake Phase	Sleep-wake times are earlier than desired/conventional. Early evening sleepiness (e.g., 6-9 PM) and early morning awakening.	📌 'Morning Larks'; older adults.
Non-24-Hour Sleep-Wake	Circadian rhythm is not entrained to a 24-hour light-dark cycle, leading to progressively later sleep times.	Most common in the blind.
Irregular Sleep-Wake	Lacks a discernible sleep-wake circadian rhythm. Sleep is fragmented into at least 3 short bouts over 24 hours.	Patients with neurodegenerative diseases (e.g., Alzheimer's).

Extrinsic Causes - Jet Lag & Shift Work

Jet Lag Disorder: Temporary mismatch between the sleep-wake cycle and a new time zone.
- Symptoms are worse with eastward travel (advancing the sleep-wake cycle).
- 📌 Mnemonic: East is a beast, West is best.
Shift Work Disorder: Insomnia and excessive sleepiness due to non-traditional work hours (e.g., night or rotating shifts).
- Leads to chronic sleep debt, impaired performance, and ↑ safety risks (e.g., accidents).

⭐ Shift work disorder is associated with a higher risk of cardiovascular disease, metabolic syndrome, and certain cancers.

Diagnosis & Management - Tuning The Clock

Diagnosis: Primarily clinical history, supported by sleep diaries or actigraphy to document the timing of sleep.
Management: Aims to realign the internal clock with the desired schedule.

⭐ For Delayed Sleep-Wake Phase Disorder, morning bright light therapy and evening low-dose melatonin are used to advance the sleep phase.

High‑Yield Points - ⚡ Biggest Takeaways

Delayed sleep-wake phase disorder ("night owls") is common in adolescents, with sleep times shifted later.

Advanced sleep-wake phase disorder ("morning larks") is seen in the elderly, with sleep times shifted earlier.

Non-24-hour sleep-wake rhythm disorder is most common in totally blind individuals lacking light cues.

Irregular sleep-wake rhythm is linked to neurodegenerative disorders (e.g., Alzheimer's).

Jet lag is typically worse and harder to treat with eastward travel.

Diagnosis is confirmed with a sleep diary or actigraphy.

Core treatments include timed light therapy and melatonin.

Continue reading on Oncourse

CONTINUE READING — FREE

or get the app

App Store|Google Play