Sleep attacks: what are they, and what diagnoses should be considered?

Sleep attacks are episodes of sudden, irresistible sleepiness that can occur in a wide range of conditions. Understanding what sleep attacks are—and which diagnoses to consider—can help you and your healthcare provider get to the root cause and find the right treatment.

What Are Sleep Attacks?
Sleep attacks are brief or prolonged bouts of overwhelming drowsiness that can strike without warning, even during activities like talking, eating or driving. They differ from normal tiredness in that:

• They come on very suddenly
• You can’t resist or delay them
• They may last from seconds to half an hour (or longer)
• You may feel disoriented on waking

Although occasional daytime sleepiness happens to everyone, recurrent sleep attacks are not normal and warrant evaluation.

Key Features to Note
When sleep attacks occur, it helps to track:

• Frequency and timing (e.g., mornings, afternoons, after meals)
• Duration of each episode
• Triggers or preceding activities
• Any associated symptoms (e.g., muscle weakness, hallucinations)
• Impact on daily life (work, driving, relationships)

Keeping a sleep diary for a week or two can be very informative for your doctor.

Possible Diagnoses to Consider
A variety of neurologic, respiratory, metabolic and psychiatric conditions can manifest with sleep attacks. Below are the main categories and examples:

1. Narcolepsy

   • Type 1 (with cataplexy) and Type 2 (without cataplexy)
   • Excessive daytime sleepiness plus one or more of: • Cataplexy (sudden loss of muscle tone triggered by emotions)
     • Sleep paralysis (temporary inability to move on falling asleep or waking)
     • Hypnagogic/hypnopompic hallucinations
   • Diagnosis:
     • Overnight polysomnogram (to rule out other sleep disorders)
     • Multiple sleep latency test (MSLT) demonstrating very short sleep latencies and sleep-onset REM periods
   • Reference: Scammell TE. Narcolepsy. Lancet Neurol. 2015.

2. Idiopathic Hypersomnia

   • Chronic, nonrefreshing sleep, long sleep durations (often >10 hours per night)
   • Daytime sleep attacks without REM-onset features of narcolepsy
   • Diagnosis:
     • Exclusion of other causes
     • MSLT may show short sleep latencies but no sleep-onset REM in most cases

3. Obstructive Sleep Apnea (OSA)

   • Episodes of upper airway collapse during sleep leading to fragmented sleep and daytime sleepiness
   • Signs/symptoms: loud snoring, witnessed apneas, nocturnal gasping
   • Diagnosis: overnight polysomnography (sleep study)

4. Medication and Substance Effects

   • Sedatives (benzodiazepines, some antidepressants)
   • Alcohol or illicit drugs
   • Polypharmacy in older adults

5. Shift Work and Circadian Rhythm Disorders

   • Misalignment of sleep–wake schedule with internal clock
   • Rotating shifts, jet lag, “social jet lag”

6. Medical and Neurologic Conditions

   • Hypothyroidism (slow metabolism, fatigue)
   • Multiple sclerosis or other demyelinating diseases
   • Parkinson’s disease or other movement disorders
   • Hepatic encephalopathy in advanced liver disease
     • Patients may experience reversal of sleep–wake cycle and daytime somnolence
     • Evaluate liver function tests; consider transient elastography (FibroScan) to assess for cirrhosis
     • Use Model for End‐Stage Liver Disease (MELD) score to gauge severity and prognosis

7. Psychiatric Conditions

   • Major depression (early morning awakening but also daytime fatigue)
   • Bipolar disorder (hypersomnia during depressive phases)

Diagnostic Approach
A systematic evaluation can distinguish among these possibilities:

1. Detailed History

   • Onset, duration, pattern of sleep attacks
   • Sleep habits, caffeine/alcohol/drug use
   • Mood symptoms, stressors

2. Physical Examination

   • Neurologic exam for signs of demyelination or movement disorders
   • ENT exam for airway abnormalities
   • Signs of liver disease (jaundice, spider angiomas, ascites)

3. Sleep Studies

   • Polysomnography to assess sleep architecture, apneas/hypopneas
   • MSLT to quantify sleepiness and detect sleep-onset REM periods

4. Laboratory Tests

   • Thyroid function, blood glucose, complete blood count
   • Liver enzymes, bilirubin, coagulation profile
   • If cirrhosis suspected: transient elastography (FibroScan) to measure liver stiffness

5. Psychiatric Screening

   • Standardized questionnaires for depression, anxiety, bipolar disorder

When to Seek Immediate Help
Sleep attacks that occur while driving or operating machinery pose a serious safety risk. If you’ve had episodes that nearly led to accidents, let your doctor know right away.

Managing Sleep Attacks
Treatment depends on the underlying cause:

• Narcolepsy or idiopathic hypersomnia
– Wake-promoting medications (modafinil, pitolisant)
– Scheduled daytime naps
– Good sleep hygiene

• Obstructive Sleep Apnea
– Continuous positive airway pressure (CPAP) therapy
– Weight loss, oral appliances, upper airway surgery

• Medication/Substance Changes
– Review and adjust sedating drugs
– Limit alcohol and recreational drug use

• Circadian Rhythm Disorders
– Bright light therapy
– Timed melatonin

• Medical Conditions
– Treat underlying disease (e.g., thyroid hormone replacement, antiviral therapy for hepatitis)
– For hepatic encephalopathy: lactulose, rifaximin, and management of liver disease

Take Control of Your Symptoms
If you’re struggling with sudden sleep attacks, keeping a sleep diary and tracking your daily routine can be a first step. You may also wish to consider doing a free, online symptom check for sleep attacks to get personalized guidance on next steps.

Speak to Your Doctor
Sleep attacks are not just “feeling sleepy”—they can signal serious disorders. Always discuss concerning symptoms with your doctor or a sleep specialist. Prompt evaluation and treatment can improve safety, quality of life and long-term health.