Hypersomnia, or excessive sleepiness, is a condition in which a person has trouble staying awake during the day. People who have hypersomnia can fall asleep at any time; for instance, at work or while they are driving.

What are the types of hypersomnia?

Hypersomnia can be primary or secondary. Primary hypersomnia occurs with no other medical conditions present. The only symptom is excessive fatigue. Secondary hypersomnia is due to other medical conditions. These can include sleep apnoea, Parkinson’s disease, kidney failure, and chronic fatigue syndrome. These conditions cause poor sleep at night, leading you to feel tired during the day.

What causes hypersomnia?

Primary hypersomnia is thought to be caused by problems in the brain systems that control sleep and waking functions. Secondary hypersomnia is the result of conditions that cause fatigue or insufficient sleep. For example, sleep apnoea can cause hypersomnia because it can cause trouble breathing at night, forcing people to wake up multiple times throughout the night. Some medications can also cause hypersomnia. Frequent drug and alcohol use may trigger sleepiness during the day. Other possible causes are low thyroid function and head injury.

Characteristics of hypersomnia

The characteristics of hypersomnia vary from one person to the next, depending on their age, lifestyle and any underlying causes. Under the International Classification of Sleep Disorders, daytime sleepiness is defined as ‘the inability to stay awake and alert during the major waking episodes of the day, resulting in unintended lapses into drowsiness or sleep’. In extreme cases, a person with hypersomnia might sleep soundly at night for 12 hours or more but still feel the need to nap during the day. Sleeping and napping may not help, and the mind may remain foggy with drowsiness. It is possible that a person with hypersomnia may have very disturbed sleep but not be aware of it.


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