What causes excessive daytime sleepiness despite a good night's sleep?

Excessive Daytime Sleepiness Despite Adequate Nocturnal Sleep

The most critical first step is to systematically rule out obstructive sleep apnea (OSA) and medication-induced hypersomnia before considering primary central disorders of hypersomnolence, as these are the most common and treatable causes of excessive daytime sleepiness despite seemingly adequate sleep. 1

Immediate Diagnostic Priorities

Rule Out Sleep-Disordered Breathing First

• OSA must be excluded before diagnosing any primary hypersomnia disorder because it is the most prevalent cause of excessive daytime sleepiness and can coexist with other conditions 1, 2
• An estimated 26-32% of adults are at risk for OSA, making this the highest-yield initial consideration 2
• Overnight polysomnography (PSG) is required to definitively exclude OSA, looking for >5 obstructive apneas per hour, frequent arousals, bradytachycardia, and oxygen desaturation 3

Medication Review is Essential

• In older adults especially, medication-induced hypersomnia is a common and frequently overlooked cause 1, 4
• Scrutinize current medications for sedating agents including benzodiazepines, opioids, antihistamines, certain antidepressants, and any CNS depressants 1, 4
• Consider recent discontinuation of stimulants or prior prolonged drug use affecting sleep-wake regulation 1, 4

Secondary Medical Causes to Evaluate

Neurological Conditions

• Parkinson's disease, stroke, multiple sclerosis, post-traumatic brain injury, and early Alzheimer's disease can all present with hypersomnia 1, 4
• Brain MRI is recommended to identify structural causes including tumors, intracranial bleeds, or demyelinating lesions 1, 4

Metabolic and Endocrine Disorders

• Check thyroid-stimulating hormone (hypothyroidism), liver function tests (hepatic encephalopathy), complete blood count, and serum chemistry 1, 4
• These conditions must be optimized before attributing sleepiness to a primary sleep disorder 1

Psychiatric Conditions

• Depression commonly presents with hypersomnia and can mimic primary hypersomnia disorders 4
• Assess for mood disorders, as treatment of the underlying psychiatric condition may resolve the sleepiness 1

Primary Central Disorders of Hypersomnolence

When to Consider After Exclusions

Once OSA is treated (or excluded), medications reviewed, and medical causes addressed, consider primary central hypersomnias if excessive sleepiness persists 1, 4

Narcolepsy Type 1 (with cataplexy)

• Key distinguishing feature: cataplexy - sudden muscle weakness triggered by emotion (laughter, anger), manifesting as leg/arm weakness, knee buckling, or dropping objects 1, 4
• Additional features include hypnagogic hallucinations (visual hallucinations at sleep onset), sleep paralysis (immobility at sleep onset/awakening), and disturbed nocturnal sleep 1, 4
• MSLT shows mean sleep latency ≤8 minutes PLUS ≥2 sleep-onset REM periods 4
• Cerebrospinal fluid hypocretin levels can confirm diagnosis without MSLT 1, 4

Narcolepsy Type 2 (without cataplexy)

• Excessive daytime sleepiness without cataplexy but may include automatic behaviors, hypnagogic hallucinations, and sleep paralysis 1, 4
• MSLT criteria identical to Type 1: mean sleep latency ≤8 minutes with ≥2 SOREMPs 4

Idiopathic Hypersomnia

• Critical MSLT distinction from narcolepsy: <2 sleep-onset REM periods despite mean sleep latency ≤8 minutes 4
• Two subtypes based on total sleep time: >10 hours (long sleep time) or 6-10 hours (without long sleep time) 1, 4
• Characterized by unrefreshing sleep, significant sleep inertia, memory lapses, concentration problems, and automatic behaviors 1, 4
• Symptoms must persist for at least 3 months 1, 4

Kleine-Levin Syndrome (Rare)

• Distinguishing feature: relapsing-remitting pattern with complete return to baseline between episodes, unlike the chronic daily sleepiness of other hypersomnias 5
• Episodes include severe hypersomnia plus cognitive/behavioral disturbances 5
• Primarily affects adolescent males (68-78%), mean onset at 15 years 5

Diagnostic Testing Algorithm

Step 1: Overnight Polysomnography

• Mandatory to exclude OSA and other sleep-disrupting conditions before proceeding to MSLT 1, 4
• Ensures adequate sleep the night before MSLT testing 4

Step 2: Multiple Sleep Latency Test (MSLT)

• Performed the day after PSG with 4-5 daytime naps at 2-hour intervals 1
• Mean sleep latency ≤8 minutes indicates objective excessive sleepiness 1, 4
• ≥2 SOREMPs = narcolepsy; <2 SOREMPs = idiopathic hypersomnia 4
• Common medications can complicate interpretation, requiring careful review 1

Step 3: Additional Testing

• Brain MRI for structural/neurological causes 1, 4
• Laboratory panel: TSH, LFTs, CBC, serum chemistry 1, 4
• CSF hypocretin-1 if narcolepsy suspected but MSLT unavailable or inconclusive 1, 4

Treatment Approach

Behavioral Modifications (All Patients)

• Maintain regular sleep-wake schedule with adequate nocturnal sleep opportunity (7-9 hours) 1
• Schedule two brief 15-20 minute naps: one around noon, another at 4:00-5:00 PM 1
• Avoid heavy meals throughout the day and eliminate alcohol use 1
• Avoid shift work, on-call schedules, prolonged driving, or jobs requiring continuous attention under monotonous conditions 1

Pharmacologic Treatment for Central Hypersomnias

First-line: Modafinil 1, 3

• Starting dose: 100 mg once upon awakening (especially in elderly) 1
• Titrate weekly as needed; typical doses 200-400 mg/day 1, 3
• Most common adverse effects: nausea, headaches, nervousness 1
• FDA-approved for narcolepsy, OSA with residual sleepiness despite CPAP, and shift work disorder 3

Alternative agents 1

• Traditional stimulants: methylphenidate, amphetamines, dextroamphetamine 1
• Sodium oxybate for narcolepsy (also treats cataplexy) 1
• Judicious caffeine use may provide adjunctive benefit 1

For cataplexy specifically 1

• Antidepressants or sodium oxybate 1

Critical Clinical Pitfalls

• Never diagnose primary hypersomnia without first adequately treating OSA if present - the sleep apnea must be controlled before assigning an independent hypersomnia diagnosis 1
• Insufficient sleep syndrome is the most common cause of excessive daytime sleepiness in the general population - ensure the patient is actually getting adequate sleep duration, not just "going to bed early" 2, 6
• "Good night's sleep" is subjective - PSG may reveal frequent arousals, sleep fragmentation, or other disruptions the patient doesn't consciously perceive 1, 7
• Medications are easily overlooked in older adults on polypharmacy - systematically review every medication for sedating properties 1, 4
• MSLT cannot be interpreted in isolation - correlation with clinical findings is essential, and the test is invalid if performed while on certain medications or without adequate prior sleep 4
• Hypersomnia in older adults may represent an early sign of neurodegenerative disease and warrants thorough evaluation 4