Hypersomnia, also known as hypersomnolence, is characterized by excessive sleepiness or uncontrollable bouts of drowsiness during the day. When these symptoms are due to a lack of sleep, a disorder such as obstructive sleep apnea, an illness, overwork or the use of certain medications, the condition is known as secondary hypersomnia.
When symptoms are not related to any particular disease or behaviour, we use the term primary hypersomnia. There are three types of primary hypersomnia: narcolepsy (see below), Kleine-Levin syndrome, a very rare neurological disease associated with cognitive and behavioural problems, as well as idiopathic hypersomnia.
This condition may take the form of chronic daytime drowsiness or extended periods of sleep (more than 10 hours per day). It may include difficulty waking up and getting out of bed, as well as confusion upon awakening, trouble staying awake during the day, extreme fatigue or attention deficit.
The causes of idiopathic hypersomnia are not well known, but this neurological disease could be due to a malfunction of the arousal systems. This rare disease affects 0.01 to 0.04% of the population, men and women alike.