Feeling excessively sleepy during the day even with a full night’s sleep may indicate idiopathic hypersomnia. This sleep-wake disorder shares similar features with narcolepsy and Kleine-Levin syndrome.
Most people experience daytime sleepiness at some point in life. Even if your clock says you’ve gotten a full night’s sleep, rest isn’t always restorative for a variety of reasons. Occasional daytime sleepiness that can be traced back to disrupted sleep overnight is natural.
But when you’re tired during the day almost every day despite quality sleep overnight, you may be living with idiopathic hypersomnia or a similar sleep-wake disorder.
Idiopathic hypersomnia is a chronic sleep-wake disorder characterized by persistent patterns of excessive daytime sleepiness (EDS) even after a full night’s sleep.
It belongs to the class of sleep-wake disorders known as central disorders of hypersomnolence (CDH), conditions that all feature EDS despite regular quality or quantity of sleep overnight.
CDH sleep-wake disorders include:
Hypersomnolence, also known as hypersomnia, is a broad term that describes the inability to stay awake or alert during typical waking hours. It’s characterized by unintentional lapses into sleep and an overwhelming need to sleep.
It’s a prominent symptom in many medical illnesses and mental health disorders, but when it occurs without a known cause, it’s referred to as “idiopathic.”
Idiopathic hypersomnia is a pattern of EDS that appears to be distinct from other CDH conditions, despite its poorly understood pathology.
Excessive daytime sleepiness despite getting enough quality sleep at night is the classic symptom of idiopathic hypersomnia, but other symptoms can include:
- daytime naps that aren’t refreshing
- long-duration nighttime sleeping (typically 9 hours or longer)
- sleep inertia, the experience of disorientation, confusion, memory impairment, poor coordination upon waking up
- hyperactivity, like excessive talking, as a way to maintain alertness
- sleep paralysis
- sleep hallucinations
- loss of balance
- poor body temperature regulation
Idiopathic hypersomnia typically develops during adolescence and early adulthood, with symptoms fluctuating in severity throughout life.
Idiopathic hypersomnia and narcolepsy are CDH conditions, sleep-wake disorders believed to be caused by central nervous system dysfunction. At this time, they’re separate diagnoses.
The division of idiopathic hypersomnia from narcolepsy is controversial, however. According to the authors of a 2020 expert review, variants of both conditions, such as narcolepsy 2 and idiopathic hypersomnia without long sleep time, may be indistinguishable from one another.
Despite some possible crossover among subtypes, review authors state differences between narcolepsy 1 and idiopathic hypersomnia clearly define them as separate conditions.
- Narcolepsy 1 is associated with low levels of hypocretin, also known as orexin, a hormone in the brain that helps regulate sleep, wakefulness, and alertness. The underlying causes of idiopathic hypersomnia aren’t yet known.
- Narcolepsy 1 typically features cataplexy, which is not a symptom of idiopathic hypersomnia.
- Sleep paralysis and hypnagogic hallucinations, intense hallucinations during sleep-wake transitions, can be experienced in both conditions but are not as common or prominent in idiopathic hypersomnia.
- EDS in idiopathic hypersomnia tends to be persistent throughout the day and does not usually feature “sleep attacks,” the sudden lapses into sleep seen in narcolepsy.
- Naps in idiopathic hypersomnia are not usually refreshing and are almost always accompanied by grogginess, disorientation, and confusion on waking. Naps in narcolepsy can be refreshing.
- According to a 2021 systematic review, narcolepsy 1 may feature greater levels of cognitive impairment compared to idiopathic hypersomnia.
- Spontaneous symptom improvement is
more commonin idiopathic hypersomnia compared to narcolepsy.
What are narcolepsy 1 and 2?
Narcolepsy 1, previously known as narcolepsy with cataplexy, is defined by low levels of the brain hormone hypocretin or the presence of cataplexy, a temporary loss of muscle tone typically triggered by strong emotions.
Narcolepsy 2, previously known as narcolepsy without cataplexy, doesn’t feature temporary loss of muscle tone and is usually associated with standard levels of hypocretin.
The causes of idiopathic hypersomnia aren’t well understood. As a central disorder of hypersomnolence, central nervous system dysfunction is thought to be involved in idiopathic hypersomnia, but no specific pathology has been identified.
Idiopathic hypersomnia can be diagnosed by a variety of healthcare professionals including primary care physicians, sleep medication specialists, and neurologists.
Using guidelines in the International Classification of Sleep Disorders, third edition (ICSD-3), your doctor will take a detailed medical history from you and discuss your current symptoms and sleep habits.
If idiopathic hypersomnia is suspected, you’ll be asked to participate in an overnight sleep study and a multiple sleep latency test (MSLT), which evaluates how quickly you fall asleep.
Under the ICSD-3, you may be diagnosed with idiopathic hypersomnia if you meet the following six criteria:
- Lapsing into sleep or the irresistible need to sleep during waking hours, daily, for at least 3 months. Supporting features include sleep inertia and unrefreshing long naps.
- Insufficient sleep syndrome has been ruled out.
- A multiple sleep latency test shows fewer than two sleep onset REM periods (SOREMPS) or no SOREMPS following a previous sleep study that showed REM sleep within 15 minutes of sleep onset.
- MLST shows an average sleep latency of 8 or fewer minutes and/or a total 24-hour sleep time of 660 minutes long or more, as indicated through a 24-hour sleep study or wrist actigraphy and a 7-day sleep log.
- No cataplexy is present.
- No other medical condition or substance can better explain symptoms of EDS or sleep test results.
In some cases, idiopathic hypersomnia may be initially diagnosed as hypersomnolence disorder, a sleep-wake disorder listed in the Diagnostic and Statistical Manual of Mental Disorders, 5th edition, text revision (DSM-5-TR), the clinical guidebook used by mental health professionals.
Hypersomnolence disorder is a broader diagnosis for conditions of EDS that don’t meet the criteria for narcolepsy.
Modafinil, a nonstimulant wake-promoting medication also used to treat EDS in narcolepsy, is considered safe and well-tolerated, with few reports of toxicity and a low risk for misuse.
It’s one of several nonstimulant wake-promoting medications that appear to increase wakefulness by influencing neurotransmitters in the brain, like dopamine.
Other medications used to treat idiopathic hypersomnia include:
In some cases of idiopathic hypersomnia, non-pharmacological interventions like lifestyle changes may help.
Your doctor may recommend:
Idiopathic hypersomnia is a sleep-wake disorder featuring EDS even after plenty of quality sleep. Its exact causes are unknown, but underlying central nervous system dysfunction is thought to play a role.
Medications are the first-line treatment for idiopathic hypersomnia, but some people may also benefit from sleep hygiene, lifestyle changes, and avoidance of substances that increase daytime sleepiness.