Excessive Daytime Sleepiness Despite Adequate Nocturnal Sleep

Diagnostic Considerations

The American Geriatrics Society recommends systematically ruling 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, 2
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 2
Medication-induced hypersomnia is a common and frequently overlooked cause, especially in older adults, and medications should be scrutinized for sedating agents including benzodiazepines, opioids, antihistamines, certain antidepressants, and any CNS depressants 2, 3

Neurological conditions such as Parkinson's disease, stroke, multiple sclerosis, post-traumatic brain injury, and early Alzheimer's disease can all present with hypersomnia, and brain MRI is recommended to identify structural causes 2, 3, 4
Metabolic and endocrine disorders, including hypothyroidism and hepatic encephalopathy, must be optimized before attributing sleepiness to a primary sleep disorder, and laboratory tests such as TSH, LFTs, CBC, and serum chemistry should be performed 4

Narcolepsy Type 1 is characterized by cataplexy, hypnagogic hallucinations, sleep paralysis, and disturbed nocturnal sleep, and is diagnosed by MSLT showing mean sleep latency ≤8 minutes PLUS ≥2 sleep-onset REM periods, or by cerebrospinal fluid hypocretin levels 2, 3, 4
Idiopathic hypersomnia is characterized by unrefreshing sleep, significant sleep inertia, memory lapses, concentration problems, and automatic behaviors, and is diagnosed by MSLT showing mean sleep latency ≤8 minutes with <2 sleep-onset REM periods 2, 3

Overnight polysomnography (PSG) is mandatory to exclude OSA and other sleep-disrupting conditions before proceeding to MSLT, and ensures adequate sleep the night before MSLT testing 3, 4
MSLT is performed the day after PSG with 4-5 daytime naps at 2-hour intervals, and mean sleep latency ≤8 minutes indicates objective excessive sleepiness, with ≥2 SOREMPs indicating narcolepsy and <2 SOREMPs indicating idiopathic hypersomnia 3, 4

Behavioral modifications, including maintaining a regular sleep-wake schedule, scheduling brief naps, avoiding heavy meals and alcohol, and avoiding shift work and prolonged driving, are recommended for all patients 4
Pharmacologic treatment for central hypersomnias includes modafinil as first-line, with alternative agents such as traditional stimulants, sodium oxybate, and judicious caffeine use, and antidepressants or sodium oxybate for cataplexy specifically 4