What is Idiopathic Hypersomnia?
Idiopathic hypersomnia (IH) is a rare, long-term sleep condition that was first identified in Prague in 1956 by Bedrich Roth. IH is generally marked by excessive sleepiness during the day, an uncontrollable need for extended naps that don’t provide refreshment, and having trouble waking up from sleep, even if you’ve had an average or more-than-average amount of night-time sleep. These symptoms should be present for at least three months.
IH is thought to have neurological origins, meaning it’s likely linked to the brain’s function. It is classified as a ‘central disorder of hypersomnolence’, which also includes conditions like narcolepsy (type 1 and type 2) and Kleine-Levin syndrome. However, the exact biological mechanisms or ‘pathophysiology’ of IH remain unclear, which makes it a difficult condition to diagnose and manage for healthcare providers. This article will summarize the cause, how common it is, its various symptoms, and its treatment in adults.
What Causes Idiopathic Hypersomnia?
The exact cause of IH, also known as idiopathic hypersomnia, is unknown. However, there are several things that may trigger it, like drastic changes in sleep-wake patterns, overuse of energy, general anesthesia (medicine used to put you to sleep for surgery), viral illnesses, or mild head trauma.
Recent studies suggest a genetic link could be involved in IH. For instance, it was found that certain forms of IH are associated with reduced signaling of orexin, a hormone that regulates wakefulness, due to a variant in the orexin producing gene. Another genetic variation, called the PER2 variant, is likewise thought to be involved.
Scientists have also found that a type of molecule called micro RNA (miRNAs), which help control gene activity in cells, could be dysfunctional in people with IH. Furthermore, recent studies suggest that IH might be linked to an abnormal immune response, which is where the body’s defense system mistakenly reacts to harmless substances. This reaction might occur between a vaccine antigen (a substance that triggers an immune response) and similar structures on nerve cells, thereby causing IH in a way similar to narcolepsy, a disorder causing excessive sleepiness.
Risk Factors and Frequency for Idiopathic Hypersomnia
Central hypersomnia is a condition that causes excessive sleepiness. One subtype, idiopathic hypersomnia (IH), is believed to stem from neurological issues and is less common than the other types, narcolepsy type 1 and type 2. IH, along with narcolepsy type 1 and type 2, and Kleine-Levin syndrome, are all classified as central disorders of hypersomnolence. Kleine-Levin syndrome typically begins in youth or the teenage years, with an average age of symptom onset of 17 and diagnosis at 30.
About one-third of the people with these conditions have family members with the same or similar conditions, suggesting a genetic component. Over the past decade, the number of IH cases has grown by 32%, affecting around 10.3 in every 100,000 people, with an equal distribution among men and women.
- Idiopathic hypersomnia (IH) is a subtype of Central hypersomnia, a condition causing excessive sleepiness.
- IH is less common than other types, like narcolepsy type 1 and type 2.
- Such conditions usually first show symptoms around 17 years of age and are typically diagnosed at around 30 years of age.
- Kleine-Levin syndrome, another type of central hypersomnia, most often affects young people or teenagers.
- About a third of cases show a family history of similar conditions, suggesting a genetic link.
- Over the past ten years, IH cases have increased by 32%, affecting about 10.3 in every 100,000 people, with no gender bias.
Signs and Symptoms of Idiopathic Hypersomnia
Idiopathic hypersomnia (IH) usually starts subtly in young individuals and progresses over a period of weeks or months. It often presents as excessive daytime sleepiness and can be difficult to wake up from sleep, a situation sometimes referred to as “sleep drunkenness”. Alongside sleepiness, people with IH often experience prolonged naps lasting more than an hour which aren’t refreshing.
There are two recognized types of this condition:
- IH with long sleep time (referred to as IHwLST), where individuals typically sleep more than 10 hours. Those with this form of IH usually see symptoms appear at a younger age, are often thinner and experience high sleep efficiency.
- IH without long sleep time (or IHwoLST), where the total sleep time isn’t as long.
Aside from excessive sleepiness, people with IHwLST can also experience difficulty waking up, fatigue, a tendency towards being more active in the evening and what is often described as “brain fog”. They may also experience automatic behaviors, sleep paralysis, and hypnogogic hallucinations. However, these symptoms are not exclusive to IH and can occur in other conditions as well.
One key point is that IH differs from narcolepsy in several ways. People with IH are more likely to take long, unrefreshing daytime naps, report a family history of sleepiness, and on conducting sleep tests, show increased levels of slow-wave sleep and a longer sleep latency.
Testing for Idiopathic Hypersomnia
If you suffer from excessive sleepiness known as idiopathic hypersomnia (IH), your doctor will try to find out the cause by ruling out other conditions first. Since this condition can’t be diagnosed merely based on your own medical history, getting tested in a sleep laboratory is very important. These tests include polysomnography (PSG), multiple sleep latency tests (MSLT), wrist actigraphy, and keeping a sleep log.
Polysomnography (PSG) is a study that records your brain waves, heart rate, and breathing as you sleep. It can also show how your muscles respond to changes in your sleep stage and record movements in your eyes and limbs. If you’re suspected for idiopathic hypersomnia, a PSG can be helpful to examine if there are any abnormalities in your sleep and what they might be.
After the PSG, the multiple sleep latency test (MSLT) is conducted. In this test, doctors check how long it takes for you to fall asleep during the day in a controlled environment. If you fall asleep in 8 minutes or less, it is considered as a sign of IH.
Using a wrist actigraphy device, which looks like a wristwatch, your sleep and wake patterns can be studied. This device gives data about how long you sleep and when you sleep and wake up. It’s often used alongside a sleep log that you keep to record your perceived sleep and wake times and any unusual occurrences during these periods.
Keep in mind, however, that various conditions like depression, insufficient sleep, use of sedating medication, or sleep-related breathing disorders can make you excessively sleepy. Therefore, it’s crucial to rule out these disorders.
According to the International Classification of Sleep Disorders (ICSD), IH can be diagnosed if you have daily periods of severe sleepiness but do not have sudden muscle weakness (known as cataplexy). Other evidence includes less than 8 minutes to fall asleep in MSLT tests or more than 660 minutes of sleep time recorded in 24-hour PSG tests or by wrist actigraphy. It is also important to confirm that your excessive sleepiness isn’t caused by insufficient sleep or any other conditions.
Treatment Options for Idiopathic Hypersomnia
Non-medical treatments like sleeping longer, taking planned naps, and behavioral therapy generally don’t work very well for idiopathic hypersomnia, a condition characterized by excessive daytime sleepiness. On the other hand, medication can be effective in managing the symptoms of this condition.
Medications that promote alertness, such as Modafinil, are recommended. Modafinil is considered the primary treatment choice for idiopathic hypersomnia, according to the latest guidelines from the American Academy of Sleep Medicine. It has been found to be very safe and equally effective as treatment in similar conditions such as narcolepsy, even in patients who don’t sleep a lot. Some common side effects reported by patients were headaches and stomach issues. In clinical trials, Modafinil significantly improved a person’s ability to stay awake longer than a placebo during a Maintenance of Wakefulness Test, and also made a noticeable improvement in patient-reported sleepiness.
Other medications have also been explored for treating idiopathic hypersomnia. For instance, a drug named Oxybate was found effective in reducing sleepiness in clinical trials conducted across multiple countries. The main side effects noted were nausea, headache, dizziness, anxiety, and vomiting. In 2021, the FDA approved the use of certain types of oxybate. The recommendation for oxybate is to start at a low dose and gradually increase it.
There are a few other medications like certain amphetamines and Pitolisant that could be helpful. Pitolisant is a drug that blocks a certain type of receptor (protein) in the brain believed to cause or exacerbate sleep disorders like idiopathic hypersomnia.
Two other options, Clarithromycin and Flumazenil, have been tested in smaller trials for idiopathic hypersomnia. Clarithromycin was found no better than a placebo in one study involving 20 participants. On the other hand, Flumazenil, given under the tongue or applied on the skin, seemed to improve sleepiness in patients whose condition didn’t respond to other treatments. However, these results need more confirmation from larger studies.
The overall clinical practice guidelines from the American Academy of Sleep Medicine recommend Modafinil as the first go-to option for adult patients with idiopathic hypersomnia, with other options like Clarithromycin, Methylphenidate, Pitolisant, and Sodium Oxybate having a conditional recommendation.
What else can Idiopathic Hypersomnia be?
There are numerous reasons why someone might experience idiopathic hypersomnia, or feeling excessively tired for no clear reason. The main contributing factors include:
- Not getting enough sleep, although extending sleep before testing can help
- Using drugs or other substances
- Suffering from a sleep-related breathing disorder – an issue which can be confirmed with a test called polysomnography
- Experiencing type 2 narcolepsy (without cataplexy) – in the early stages of the condition, a specific symptom (called SOREMPs) may not be noticeable during testing
- Having a psychiatric disorder, such as depression. Despite the disorders, the average sleep latency (the amount of time it takes to fall asleep) can still be normal
- Having a movement disorder, such as periodic limb movement disorder
- Suffering from chronic fatigue syndrome, which leads to persistent tiredness that doesn’t get better with rest or sleep
- Having a chronic medical condition, or suffering from hypercapnia or Trypanosomiasis. These are usually identified through a patient’s medical history, a physical exam, and lab testing
- Being affected by a neurological disorder, like Alzheimer’s or Parkinson’s disease
Knowing these potential causes can help doctors to carry out the right tests and reach an accurate diagnosis.
What to expect with Idiopathic Hypersomnia
Most people with IH, or Idiopathic Hypersomnia, a condition that causes excessive daytime sleepiness, usually maintain a stable condition. Interestingly, spontaneous improvement is more common in IH than in Narcolepsy. A recent research conducted in Japan observed that people with IH who are older than 35 tended to have a higher rate of metabolic syndrome, a cluster of conditions that increase the risk of heart disease, stroke, and type 2 diabetes.
Long daytime naps of more than an hour have been associated with a greater risk of stroke and high blood pressure. This is after considering other risk factors for heart disease and stroke. For those under 60, napping on most days could raise their risk of developing high blood pressure by 20%, compared to those who rarely or never nap.
Possible Complications When Diagnosed with Idiopathic Hypersomnia
Excessive sleepiness during the day can pose risks to both individuals and those around them. This sleepiness can contribute to automatic behaviors, which can increase the chance of car accidents. Also, oxybate, a medication used to treat these symptoms, is strictly regulated in the United States due to its potential misuse as a “date-rape” drug under controlled substances category Schedule III.
Dangerous Consequences:
- Risks to individual and others due to excessive daytime sleepiness
- Higher possibility of car accidents
- Potential misuse of oxybate as a “date-rape” drug
Preventing Idiopathic Hypersomnia
Patients who have Idiopathic Hypersomnia (IH) – which is an excessive sleep disorder – should be made aware of the potential risks of driving and operating heavy machinery. It’s vital that they closely monitor their condition and manage their medication use with regular check-ins. In our medical practice, we aim to see these patients – at a minimum – every six months, although sometimes we see them more frequently. During these visits, we ensure their prescriptions for controlled substances are renewed and check on how they’re managing in work and social situations. We also assess how well their daytime sleepiness is controlled and if they’re taking their medications as recommended. This helps us ensure the best possible care for their condition.
