The 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.