Somnolence

Somnolence is a state of an increased propensity to sleep or a strong urge to fall asleep, often described as daytime sleepiness. It is a symptom rather than a disease and can range from mild to disabling. Somnolence is distinct from fatigue, which reflects low energy or motivation; somnolence specifically concerns wakefulness and the likelihood of falling asleep.

Common causes include inadequate or disrupted sleep (short sleep duration, shift work, jet lag), sleep disorders such as obstructive sleep apnea, narcolepsy, hypersomnia, and restless legs syndrome, and medications or substances (benzodiazepines, opioids, sedatives, alcohol, antihistamines). Medical conditions like thyroid disease, diabetes, liver or kidney disease, infections, and psychiatric disorders such as depression or anxiety can contribute. Age, pregnancy, and neurological disorders may also play a role.

Diagnosis relies on history and examination, supported by tools such as the Epworth Sleepiness Scale and sleep diaries. When indicated, actigraphy or overnight polysomnography can assess sleep quality and identify disorders. A multiple sleep latency test may help diagnose narcolepsy or other hypersomnias and rule out other causes of daytime sleepiness.

Management targets the underlying cause and the level of wakefulness. Interventions include improving sleep hygiene, regularizing sleep schedules, and minimizing or adjusting sedating medications. Treatable sleep disorders may require specific therapies (for example, continuous positive airway pressure for obstructive sleep apnea; stimulants or wake-promoting agents for narcolepsy) under medical supervision. Short, planned daytime naps may be appropriate in some cases. Safety considerations include reduced alertness and impaired driving.

Prognosis varies with the cause; addressing underlying conditions often improves wakefulness and quality of life, while untreated somnolence can increase the risk of accidents and functional impairment.