Hypersomnia: excessive sleepiness, causes, symptoms and treatment

Hypersomnia is the medical word for excessive sleepiness: finding it very hard to stay awake in the day, or needing far more sleep than other people. It is a symptom with many possible causes rather than a single condition, although the term is also used for a small group of rare sleep disorders in which the brain’s control of sleeping and waking is affected.

GOV.UK, in its driving guidance, describes excessive sleepiness as having had difficulty concentrating and found yourself falling asleep, for example while at work, watching television or driving. That is different from ordinary tiredness, although the NHS notes that everyone feels tired sometimes and that it is when you are tired all the time without knowing why that it may signal a problem.

It is worth separating three things that people mean by the word: being tired (low energy), being sleepy (struggling to stay awake) and sleeping for very long periods. A GP will ask about all three.

The main symptom is persistent sleepiness in the daytime despite what should be enough sleep. Beyond that, the picture depends on the cause.

Narcolepsy UK describes the features of idiopathic hypersomnia: a long sleep duration of 11 hours or more, not feeling refreshed on waking, prolonged confusion, disorientation and irritability on waking (sleep inertia, a foggy state that can last several hours), excessive daytime sleepiness with the need for daytime naps, and automatic behaviour during periods of sleepiness.

The NHS lists the symptoms of narcolepsy as feeling sleepy during the day and having difficulty staying awake, falling asleep suddenly, sudden muscle weakness (cataplexy) which may be triggered by emotions such as anger, sadness or laughter, difficulty concentrating, waking often in the night, being unable to move or speak when falling asleep or waking (sleep paralysis), and dreaming a lot with dreams that seem real or intense.

• feeling very tired or sleepy during the day, despite a full night’s sleep

• long sleep at night and difficulty waking up

• confusion or grogginess on waking that lasts a long time

• needing naps, often without feeling refreshed

• difficulty concentrating

• in narcolepsy: cataplexy, sleep paralysis and vivid dreams

The NHS says common causes of tiredness and fatigue include not getting enough sleep or finding it hard to get to sleep, an unhealthy lifestyle, stress, depression and life challenges, hormonal changes (such as in puberty, pregnancy or the menopause), some illnesses such as glandular fever and COVID-19, and some medical treatments and medicines.

It also lists particular conditions that can cause tiredness, matched with their typical symptoms. Of these, obstructive sleep apnoea is one to think about if sleepiness comes with loud snoring or noises such as gasping or choking in sleep.

Rarer causes sit within sleep medicine. The NHS says the cause of narcolepsy is not known, but it happens when the brain cannot control sleeping and waking normally, and that you may be more likely to have it if a close relative has it or you have certain rare genetic conditions. Narcolepsy UK says the cause of idiopathic hypersomnia is not yet known and that there is currently no cure.

A GP will usually ask about your lifestyle, sleep habits, medicines and medical history. The NHS says tests for general tiredness may include blood tests to check for anaemia, diabetes or an overactive thyroid, and that a GP may refer you to a specialist if they do not know the cause.

If a rarer sleep disorder is suspected, you are referred to a sleep specialist. For narcolepsy, the NHS says it can help to keep a diary of your symptoms and that you will usually be offered tests such as polysomnography (measuring your breathing, brain activity, heart rate and movement overnight), a multiple sleep latency test (monitoring how quickly you fall asleep) and sometimes a lumbar puncture. Narcolepsy UK says diagnosis of idiopathic hypersomnia will usually require an overnight sleep test and a multiple sleep latency test in a specialist sleep clinic.

Sleep apnoea is investigated separately. The NHS says you may be given devices to wear overnight that check your breathing and heartbeat, and that this can usually be done at home.

Treatment depends on the cause. The NHS says treatment for tiredness depends on the cause and may include talking therapies such as CBT, advice on getting better sleep and advice on relaxing or changing lifestyle, and that sleep apnoea is often treated with a CPAP machine, which is provided free on the NHS if needed.

For narcolepsy, the NHS says there is currently no cure but treatment and lifestyle changes help. You will usually be referred to a specialist, be advised on sleep management (a regular bedtime routine, going to bed and waking at the same time each day, planned naps during the day and getting enough sleep at night), and may be prescribed medicines to help you stay awake during the day or to prevent sudden muscle weakness.

For idiopathic hypersomnia, Narcolepsy UK says treatment involves wake-promoting medicines like modafinil and stimulants like methylphenidate, with lifestyle changes that can be particularly challenging to implement. Because both are specialist decisions, the choice of medicine should come from a sleep specialist rather than from self-treatment.

GOV.UK says you must tell the DVLA if you have confirmed moderate or severe obstructive sleep apnoea with excessive sleepiness, narcolepsy or cataplexy, or any other sleep condition that has caused excessive sleepiness for at least 3 months, including suspected or confirmed mild sleep apnoea. You must not drive until you are free from excessive sleepiness or your symptoms are under control and you are strictly following any necessary treatment. You can be fined for not telling the DVLA about a condition that affects your driving.

The NHS says in narcolepsy that sudden sleeping or falling is not usually harmful in itself but can cause accidents or injuries, and that you may need to avoid activities at home or work that could be dangerous if you fall asleep suddenly.

The NHS says to see a GP if you have felt tired for a few weeks and are not sure why, your tiredness affects your daily life, you feel tired and have other symptoms such as weight loss or mood changes, or you have been told you make gasping, snorting or choking noises when asleep.

For narcolepsy specifically, the NHS says to see a GP if you feel tired all the time for no reason, fall asleep suddenly during the day, or have sleep problems that worry you or affect your life. If you have fallen asleep while driving or nearly done so, do not drive and speak to a doctor promptly.

The NHS says symptoms of narcolepsy usually start in children and young adults, and Narcolepsy UK says idiopathic hypersomnia most frequently starts in the teens and can damage schooling, work and relationships, so it is important to get a diagnosis as soon as possible after symptoms begin.

The NHS lists pregnancy among the hormonal changes that can cause tiredness. The UK sources we read do not give separate guidance on treating hypersomnia disorders in pregnancy, which is a decision for a specialist.

On the NHS, the route is a GP appointment first, with blood tests and a review of sleep and medicines, then referral to a sleep specialist if a sleep disorder is suspected. The NHS says that if a GP thinks you may have narcolepsy you will need to see a sleep specialist, and that a GP may refer you if they do not know the cause of tiredness.

Sleep studies can also be arranged privately. The type of test and who interprets it matter more than the setting, so take any results to your GP. Narcolepsy UK provides information and support, including a helpline listed by the NHS.