Excessive sleepiness

Excessive daytime sleepiness: When sleep doesn't bring rest

Excessive daytime sleepiness (hypersomnia) is a condition in which a person feels strong sleepiness during the day despite, apparently, sufficient duration of nighttime sleep. It is not just fatigue or the desire to nap after lunch. It is an overwhelming need for sleep that interferes with normal functioning, work, learning and can be dangerous (for example, while driving a car). Hypersomnia can be a symptom of many sleep disorders.

Why doesn't nighttime sleep restore?

Most often the cause lies in poor quality nighttime sleep, which a person may not even suspect.

• Obstructive sleep apnea syndrome (OSA): This is the main cause of pathological daytime sleepiness. Repeated breathing pauses cause hundreds of micro‑awakenings during the night. The person does not remember them, but their sleep becomes superficial and does not reach deep, restorative stages.
• Restless legs syndrome and periodic limb movements: Constant leg movements also fragment sleep.
• Chronic insomnia: Although it seems opposite, prolonged poor nighttime sleep inevitably leads to daytime sleepiness.
• Circadian rhythm disorders: Mismatch between the internal clock and the social schedule (e.g., shift work).

Other causes of hypersomnia

Sometimes the cause is not sleep quality but other conditions:

• Narcolepsy: A rare neurological disorder characterized by "sleep attacks" — sudden, uncontrollable episodes of falling asleep during the day.
• Medication side effects: Many drugs (antihistamines, antidepressants, antiepileptics) can cause sleepiness.
• Mental disorders: In depression hypersomnia can be one of the symptoms.