“I slept 10 hours but I am tired and had sleep paralysis”…it may not be simple fatigue

 Jin-woo, who has moved up to his final year of high school this year, has a lot on his mind as the new term approaches. He needs to concentrate harder on his studies from now on, but he sleeps far too much. Even after more than 10 hours of sleep he nods off in class, and when he wakes from a nap he does not feel refreshed. He feels drowsy and foggy all day long. His parents, who used to tell him that ‘sleep is the best medicine’, have now grown worried too and brought Jin-woo to the hospital. At the hospital, however, Jin-woo was diagnosed with ‘hypersomnia’, one of the sleep disorders.

‘Hypersomnia’ is rising among adolescents
Sleep disorders are common enough that about 20% of the whole population experiences them. In modern society, with rising stress and greater use of electronic devices, the number of people with sleep disorders is increasing further. Sleep disorders include insomnia, in which a person cannot sleep; sleep apnea, in which breathing stops or decreases during sleep; and hypersomnia, in which a person sleeps excessively.

Patients with hypersomnia, like Jin-woo, are becoming more numerous. According to Health Insurance Review and Assessment Service statistics, the number of hypersomnia patients passed 2,000 for the first time in 2022 and rose to 2,583 in 2024. Notably, many of those diagnosed with hypersomnia are adolescents and young adults, from their teens through their 20s.

Sleeping a lot may not be a matter of willpower
Hypersomnia is divided into idiopathic hypersomnia and narcolepsy. With idiopathic hypersomnia, you feel sleepy all day and do not feel refreshed even after sleeping more than 10 hours and taking a nap. Waking up in the morning also takes a very long time and is difficult. If these symptoms continue for several months, hypersomnia should be suspected.

Hong, Seung Bong, Director of Neurology at St. Peter's Hospital, advised, “Idiopathic hypersomnia is easily mistaken for a lack of willpower or laziness.” He added, “Left untreated, the condition can affect schoolwork through sleepiness, lateness and poor concentration, so care is needed.”

Narcolepsy is a condition in which you suddenly drop off to sleep — just like that — in everyday life, such as while talking or eating. Unlike idiopathic hypersomnia, a nap can leave you feeling refreshed. Patients also commonly experience sleep paralysis, what is usually described as ‘being pinned down by a ghost’. Narcolepsy can be divided into type 1, which involves excessive daytime sleepiness (abnormal sleepiness during the day) together with cataplexy (a loss of strength when there is emotional stimulation such as laughing or becoming angry), and type 2, which involves only daytime sleepiness.

The cause of idiopathic hypersomnia has not been clearly identified; family history and autoimmune abnormalities have only been reported as possible factors. Narcolepsy, by contrast, is known to arise when the body lacks hypocretin, the neurohormone that promotes wakefulness.

How is hypersomnia diagnosed?
Hypersomnia is diagnosed with overnight polysomnography and the multiple sleep latency test. Because these tests are carried out while you actually sleep, they take about two days and one night. Overnight polysomnography checks for other sleep disorders that cause excessive daytime sleepiness, such as sleep apnea. The multiple sleep latency test is then performed during the following day, measuring the mean sleep latency (the time taken to fall asleep) and the REM sleep latency (the time from falling asleep to REM sleep).

Once hypersomnia is diagnosed, treatment is needed. Treatment begins with medication that activates neurotransmitters to maintain alertness and prevent daytime sleepiness. Alongside this, lifestyle and behavioral therapy is provided, covering proper sleep, exercise, a healthy diet and regular naps.

Keeping habits that support sound sleep
Even if you do not have hypersomnia, it is good to keep to lifestyle habits that support sound sleep. First, go to sleep and wake up at set times to maintain your sleep rhythm. Also, from at least 1 hour before you go to sleep, darken the sleeping environment — by switching to a night light, for example — so that your body can prepare for sleep in advance. From 30 minutes beforehand, refrain from using electronic devices as far as possible. Instead, relaxing activities such as stretching, meditation and reading can help you sleep.

Keep naps short, within 15 minutes, and avoid late-afternoon naps. Cutting back on caffeinated drinks, taking up a healthy hobby that relieves stress, and increasing daytime activity such as exercise all help you sleep well.