Glossary

Our glossary is here to help you understand the information contained on our website. You can also see the glossary definitions by clicking on the underlined words on our web pages.

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  • a

  • Absolute risk is your actual risk over a time period. Many reports in the media present risk results as relative risk reductions (relative risk is used to compare risk in two different groups of people) rather than absolute risk reductions. This often makes treatments seem better than they actually are. Similarly, presenting relative risk increases of side effects/negative effects can make them seem worse than they actually are. Read more HERE.

  • Actigraphy measures body movements. An actigraph looks like an oversized watch, and you wear it on your nondominant wrist (that means if you’re right-handed, you wear it on your left wrist). When combined with a sleep diary, actigraphy helps measure patterns in your sleep-wake cycle.

  • In medicine, an adjunct is a supplement to another main therapeutic treatment.

  • An agonist is a chemical that binds to and activates a receptor. The result is a biologic response — an action. (An antagonist is the opposite of an agonist.)

  • An allele is a variant form of a gene. Each gene resides at a specific locus (location on a chromosome) in two copies; one copy of the gene is inherited from each parent. The copies, however, are not necessarily identical. When the copies of a gene differ from each other, they are known as alleles. A given gene may have multiple different alleles, but only two alleles are present at the gene’s locus in any individual. (Read more HERE.)

  • Allosteric modulators are substances that indirectly influence or modulate the effects of an agonist at a receptor. For example, with respect to the GABAA receptor, positive allosteric modulators increase the activity of the GABAA receptor protein in the central nervous system of mammals. (Examples of positive allosteric modulators include alcohol, benzodiazepines [such as Valium], benzodiazepine-receptor agonists [such as Ambien or Lunesta], anesthetic gases, and propofol.) In contrast, negative allosteric modulators inhibit or decrease the activity of the GABAA receptor protein. (Examples of negative allosteric modulators or inhibitors of GABAA activity are flumazenil, bicuculline, pentylenetetrazol, and gabazine.)

  • Amphetamines are stimulant medicines that doctors can use to treat excessive daytime sleepiness (EDS), severe sleep inertia, and cataplexy. They include:

    • Dextroamphetamine (such as Dexedrine, ProCentra, and Zenzedi)
    • Amphetamine (such as Adzenys ER, Adzenys XR, Dyanavel XR, and Evekeo)
    • Combination dextroamphetamine-amphetamine (such as Adderall, Biphetamine, and Mydayis)
      Lisdexamfetamine (such as Vyvanse)

  • Anesthesia is a treatment that stops pain, awareness, or memory during a medical procedure.

    There are different types of anesthesia:

    • General anesthesia is a combination of medicines that puts you to sleep before a surgery or tests. It causes complete loss of consciousness.
    • Conscious sedation is a type of anesthesia that usually wears off quickly and is used for short, uncomplicated procedures. You may stay awake, but may not be able to speak and will likely feel drowsy and not remember much afterward.
    • A local or regional anesthetic (nerve block) numbs a small area or a larger part of your body and is usually given as a shot.

  • An anomaly is something that deviates from what is standard, normal, or expected. It is abnormal.

  • An antagonist is a chemical that binds to and inactivates a receptor. The result is a blocking of a biologic response. (An antagonist is the opposite of an agonist.)

  • Anterograde amnesia is a type of memory loss where your brain can’t form new memories. It’s often temporary.

  • An insurance appeal is a request for your insurer to reconsider their decision to deny coverage or payment, such as for your health care or disability income.

  • In autoimmune diseases, your immune system makes your body attack itself.

  • An automatic behavior is a behavior or action that someone does without full awareness or control. The action may not make sense, such as putting a cereal bowl in the dryer instead of the dishwasher. They may not remember some or all the action, such as having a conversation.

    Automatic behaviors often happen when someone with a hypersomnia sleep disorder is partially asleep, like when they’re feeling a strong pressure to go to sleep or have recently woken up. Automatic behaviors may last a few minutes or up to an hour. People with sleep-related automatic behavior may appear sleepy but can be alerted and answer questions appropriately.

  • When you have autonomic dysfunction (sometimes called dysautonomia), you may have problems with any part of your autonomic nervous system (ANS). This can lead to symptoms like headache, orthostatic intolerance (when your body struggles to adapt to being upright), fatigue (feeling weak and tired), dizziness, heart palpitations (racing or fluttering heartbeat), shortness of breath, poor body temperature control, nausea and other digestive symptoms, urinary problems, and problems with the blood vessels in your hands and feet.

    Your ANS controls several basic body functions, such as heart rate, blood pressure, body temperature, breathing rate, digestion, skin sensation, bladder, sweat glands, and metabolism. These body functions are involuntary, which means you usually can’t consciously control them.

    Your ANS is made up of 3 parts:

    • Your sympathetic nervous system controls your body’s “fight or flight” response by raising your heart rate and releasing energy

    • Your parasympathetic nervous system controls your involuntary body processes during relaxation and other ordinary situations, including slowing down your heart rate and lowering your blood pressure

    • Your enteric nervous system controls your digestive (gastrointestinal) system

  • Autonomic reflex screen (ARS) testing includes a variety of tests to measure how heart rate and blood pressure change in response to changes in position (e.g., tilt table testing) and breathing. The testing may also evaluate how the nerves that regulate sweat glands respond to stimulation.

  • Autonomic reflex screen (ARS) testing includes a variety of tests to measure how heart rate and blood pressure change in response to changes in position (e.g., tilt table testing) and breathing. The testing may also evaluate how the nerves that regulate sweat glands respond to stimulation.

  • b

  • Baclofen is a GABA-B receptor agonist medicine that doctors usually use to treat muscle spasms. Doctors sometimes use baclofen to treat excessive daytime sleepiness (EDS), sleep disruption, and cataplexy.

    Brand names include: Baclodol, Baklofen, Beklo, Clofen, Flexibac, Gablofen, Kemstro, Liofen, Lioresal, Lyflex, Lyvispah, Muslofen, Ozobax, and Sclerofen.

  • The Beck Depression Inventory (BDI) is a widely used 21-item questionnaire for measuring severity of depression.

  • The Beck Depression Inventory (BDI) is a widely used 21-item questionnaire for measuring severity of depression.

  • Our slogan “Let’s get #BeyondSleepy” is a metaphor intended to provoke a discussion or consideration of the many ways that idiopathic hypersomnia and related disorders affect people. We strive to “get beyond” all the life-altering symptoms, including “beyond sleepiness,” “get beyond” the stigma, “get beyond” the lack of understanding, “get beyond” misdiagnosis and length of time to a diagnosis, and “get beyond” off-label treatments.

  • A biomarker (which is a short for biological marker) is a substance that is found in blood, other body fluids, or tissues that indicates a normal or abnormal process, a condition or disease, or the effects of treatment.

  • A birth control implant is a tiny, thin rod about the size of a matchstick that a doctor inserts in your arm. The implant releases the hormone progestin into your body to prevent pregnancy for up to 5 years.

  • A birth control patch is a small patch worn on your skin. It gives estrogen and progestin hormones through your skin to help prevent pregnancy.

  • Birth control pills (oral contraceptives) are a type of medicine with hormones that you take by mouth to help prevent pregnancy.

    The 2 types of birth control pills are:

    • Combination pills (combined oral contraceptives or COCs), which have both estrogen and progestin hormones
    • Progestin-only pills (minipills or POPs), which only have a progestin hormone

  • Brain fog is a condition that makes it hard to think clearly. You might feel confused, forgetful, or unable to focus. This can make it hard to make decisions or do daily tasks.

  • c

  • Carnitine is a substance your body makes in your liver and kidneys and stores in your skeletal muscles, heart, brain, and sperm. Carnitine helps turn fat into energy. Some people don’t make enough carnitine, or their bodies can’t use it correctly. Doctors may recommend carnitine supplements (such as Carnitor) to treat excessive daytime sleepiness (EDS).

  • Typical cataplexy is a sudden loss of muscle strength that happens equally on both sides of your body. It’s usually triggered by strong emotions, such as laughing, crying, or terror. It usually affects the face (sagging jaw), neck (head drop), or legs (buckling knees). Typical cataplexy episodes last less than 2 minutes (usually less than 30 seconds). People with this symptom are fully conscious and aware, even if they don’t look like it.

    Typical cataplexy is one of the main defining symptoms of narcolepsy type 1 (NT1), but atypical cataplexy is much less strongly associated with NT1. Atypical cataplexy is different in several ways, such as that it may last longer and happen on only one side of your body. To learn more, visit “How is typical cataplexy diagnosed in adults?” on our diagnosis web page for doctors.

  • Cerebrospinal fluid (CSF) is a clear, colorless fluid that surrounds your brain and spinal cord. Its main job is to protect your brain and spinal cord by acting as a barrier and shock absorber. CSF also removes waste products, antibodies (substances that help your body fight infections), chemicals, and disease-causing substances from your brain and spinal cord.

  • Cerebrospinal fluid (CSF) is a clear, colorless fluid that surrounds your brain and spinal cord. Its main job is to protect your brain and spinal cord by acting as a barrier and shock absorber. CSF also removes waste products, antibodies (substances that help your body fight infections), chemicals, and disease-causing substances from your brain and spinal cord.

  • The CCR1 and CCR3 (C-C chemokine receptor 1 and 3) genes are involved in regulating the body’s response to bacteria, viruses, and other substances that the body perceives to be harmful or not a part of itself (that is, “foreign”).

  • The CCR1 and CCR3 (C-C chemokine receptor 1 and 3) genes are involved in regulating the body’s response to bacteria, viruses, and other substances that the body perceives to be harmful or not a part of itself (that is, “foreign”).

  • Circadian rhythms are the physical, mental, and behavioral changes you experience over a 24-hour cycle. Light and dark have the biggest influence on circadian rhythms, but food intake, stress, physical activity, social environment, and temperature also affect them.

    Circadian rhythms influence important functions in your body, such as:

    • Sleep patterns
    • Hormone release
    • Appetite and digestion
    • Temperature

  • Clarithromycin is an antibiotic and a GABA-A receptor antagonist medicine. Doctors sometimes use it to treat excessive daytime sleepiness (EDS).

    Brand names include Biaxin and Biaxin XL.

  • There are two types of CGI (Clinical Global Impression) scales, which vary depending on the precise issue the professional or researcher is assessing. The first is the Clinical Global Impression-Severity (CGI-S) scale, which is a 7-point scale that healthcare professionals or researchers (clinicians) use to rate the patient’s severity of illness at the time of assessment, relative to the clinician’s past experience with patients who have the same diagnosis. Responses include: 1) normal or not at all ill; 2) borderline mentally ill; 3) mildly ill; 4) moderately ill; 5) markedly ill; 6) severely ill; or 7) among the most extremely ill patients. The second scale is the Clinical Global Impression-Improvement scale (CGI-I), which is a 7-point scale that requires the clinician to assess how much the patient's illness has improved or worsened relative to a baseline state at the beginning of an intervention. Responses include: 1) very much improved; 2) much improved; 3) minimally improved; 4) no change; 5) minimally worse; 6) much worse; or 7) very much worse.

  • There are two types of CGI (Clinical Global Impression) scales, which vary depending on the precise issue the professional or researcher is assessing. The first is the Clinical Global Impression-Severity (CGI-S) scale, which is a 7-point scale that healthcare professionals or researchers (clinicians) use to rate the patient’s severity of illness at the time of assessment, relative to the clinician’s past experience with patients who have the same diagnosis. Responses include: 1) normal or not at all ill; 2) borderline mentally ill; 3) mildly ill; 4) moderately ill; 5) markedly ill; 6) severely ill; or 7) among the most extremely ill patients. The second scale is the Clinical Global Impression-Improvement scale (CGI-I), which is a 7-point scale that requires the clinician to assess how much the patient's illness has improved or worsened relative to a baseline state at the beginning of an intervention. Responses include: 1) very much improved; 2) much improved; 3) minimally improved; 4) no change; 5) minimally worse; 6) much worse; or 7) very much worse.

  • A clinical trial is one of two main types of clinical studies, which are research studies involving human participants. A clinical trial tests (or tries out) an intervention – a potential drug, medical device, activity, or procedure. It also is referred to as an interventional clinical study. The other main type of clinical study is an observational study. In an observational study, researchers observe participants on their current treatment plan and track health outcomes. Read more HERE.

  • Cognitive behavioral therapy (CBT) is a form of therapy that is goal-oriented; it involves examining and changing your behavior and patterns of thoughts, with the guidance and coaching of a therapist specially trained in CBT. A number of clinical studies have shown CBT to be effective for many conditions, including depression and anxiety. Read more about Getting Support from a Mental Health Professional.

  • Cognitive behavioral therapy (CBT) is a form of therapy that is goal-oriented; it involves examining and changing your behavior and patterns of thoughts, with the guidance and coaching of a therapist specially trained in CBT. A number of clinical studies have shown CBT to be effective for many conditions, including depression and anxiety. Read more about Getting Support from a Mental Health Professional.

  • The term comorbid refers to two or more different medical conditions, which may or may not be related, occurring at the same time.

  • Complex sleep apnea is a relatively rare sleep disorder in which central apneas either persist or emerge once obstructive sleep apnea is treated (usually with CPAP or BiPAP). The underlying cause of complex sleep apnea is not well understood but is thought to involve the peripheral chemoreceptors and brain stem responses. Read more about complex sleep apnea HERE.

  • A condom is a form of birth control. It’s a thin, stretchy pouch you wear during sex to help prevent pregnancy and protect against sexually transmitted infections (STIs). An external condom is for the penis. An internal condom is for the vagina. Don’t use internal and external condoms together, since that can cause tearing.

  • In an experiment or clinical trial, control subjects make up a group of participants who have characteristics similar to those of the treatment group, but they do not receive the treatment being studied. In an observational study, the control subjects have similar characteristics as those participants being studied, except that they do not have the symptom, disease, syndrome, or disorder being studied.

  • In a crossover study, each participant receives both the placebo and the active drug for a defined period of time. The order in which people receive the different treatments is determined randomly, and the responses that participants have to each of the different treatments are compared. Crossover studies can be double-blind, single-blind, or unblinded.

  • d

  • DBSM is the acronym for Diplomate in Behavioral Sleep Medicine. Learn more about this credential via the Board of Behavioral Sleep Medicine.

  • Delirium is a change in mental state (or state of mind) that may happen quickly and suddenly. Symptoms include:

    • Confusion
    • Agitation (unrest)
    • Hallucinations (seeing, hearing, or feeling something that isn’t there)

  • Derealization is the ongoing feeling that:

    • Things around you aren't real
    • You're watching yourself from outside your body (also called depersonalization)

  • The Diagnostic and Statistical Manual of Mental Disorders (DSM) is a reference book that helps doctors figure out if someone has a mental disorder or neurologic disorder (disorder of the brain or nerves), including sleep disorders. The DSM is published by the American Psychiatric Association, and the 2022 DSM-5-TR (text revision) is the most recent version.

  • The Diagnostic and Statistical Manual of Mental Disorders (DSM) is a reference book that helps doctors figure out if someone has a mental disorder or neurologic disorder (disorder of the brain or nerves), including sleep disorders. The DSM is published by the American Psychiatric Association, and the 2022 DSM-5-TR (text revision) is the most recent version.

  • A contraceptive diaphragm is a form of birth control. It’s a soft, shallow cup that’s placed inside the vagina to help prevent pregnancy. For it to work well, it must be used with a cream or gel that kills sperm (spermicide) and left in for at least 6 hours after sex.

  • In medicine, the process of considering other diagnoses which have similar symptoms or signs.

  • Disinhibition is trouble controlling impulses. This can lead to behavior problems, such as aggressive outbursts, hyperphagia, or hypersexuality.

    • Hyperphagia (also called megaphagia or polyphagia) is extreme hunger that is hard to satisfy, which can lead to eating too much or too fast
    • Hypersexuality is intense, ongoing sexual thoughts, urges, or behaviors

  • Disrupted nighttime sleep (DNS) is when you wake up many times in a night. You may not notice when this happens, but it can make your sleep less restful and you may wake up feeling tired and unrefreshed. Your sleep studies may show arousals (wake-ups) from sleep or a high number of shifts (changes) between different stages of sleep.

  • Disrupted nighttime sleep (DNS) is when you wake up many times in a night. You may not notice when this happens, but it can make your sleep less restful and you may wake up feeling tired and unrefreshed. Your sleep studies may show arousals (wake-ups) from sleep or a high number of shifts (changes) between different stages of sleep.

  • A double-blind trial or study is one in which neither the people who are doing the experiment nor the people who are the subjects of the experiment know which of the groups being studied is receiving the substance under investigation (active group) or is receiving the placebo (control group).

  • Dyskinesias are uncontrollable body movements. They can affect just one part of your body, like your head or your arm, or your entire body.

  • e

  • An effector cell is a muscle, gland or organ cell that is capable of responding to a stimulus.

  • Electroencephalography (EEG) is the measurement and recording of the brain's electrical activity by a typically non-invasive monitoring method.

  • Electroencephalography (EEG) is the measurement and recording of the brain's electrical activity by a typically non-invasive monitoring method.

  • With respect to genetics, encoding means that our genes provide the blueprint or code for arranging amino acids so that they make proteins in our bodies.

  • An endogenous substance originates from or is produced within an organism (such as the human body), tissue or cell. (The opposite of endogenous is exogenous.)

  • The Epworth Sleepiness Scale (ESS) is a set of questions that measures how likely you are to fall asleep in each of 8 situations. For example, you might respond to a question about dozing with an answer of 0 (would never doze), 1 (slight chance of dozing), 2 (moderate chance of dozing), or 3 (high chance of dozing). Your responses to all of the eight questions are combined for a final score, which can range between 0 and 24. Higher scores indicate higher levels of daytime sleepiness. Most doctors and scientists consider scores of 10 or higher to indicate abnormal sleepiness.

  • The Epworth Sleepiness Scale (ESS) is a set of questions that measures how likely you are to fall asleep in each of 8 situations. For example, you might respond to a question about dozing with an answer of 0 (would never doze), 1 (slight chance of dozing), 2 (moderate chance of dozing), or 3 (high chance of dozing). Your responses to all of the eight questions are combined for a final score, which can range between 0 and 24. Higher scores indicate higher levels of daytime sleepiness. Most doctors and scientists consider scores of 10 or higher to indicate abnormal sleepiness.

  • Etiology refers to the cause or basis of a disease or condition.

  • The European Medicines Agency (EMA), which was established in 1995, is a decentralized agency of the European Union, located in London. The Agency is responsible for the scientific evaluation of medicines developed by pharmaceutical companies for use in the European Union. (It is similar to the Food & Drug Administration [FDA] in the United States.)

  • The European Medicines Agency (EMA), which was established in 1995, is a decentralized agency of the European Union, located in London. The Agency is responsible for the scientific evaluation of medicines developed by pharmaceutical companies for use in the European Union. (It is similar to the Food & Drug Administration [FDA] in the United States.)

  • Excessive daytime sleepiness (EDS) is a strong daytime sleepiness or need to sleep during the day, even with enough sleep the night before.

  • Excessive daytime sleepiness (EDS) is a strong daytime sleepiness or need to sleep during the day, even with enough sleep the night before.

  • An exogenous substance originates from or is produced outside an organism (such as the human body), tissue or cell. (The opposite of exogenous is endogenous.)

  • f

  • Fatigue is a lack of physical or mental energy. It’s when you feel tired or exhausted.

    Fatigue is different from sleepiness:

    • Sleepiness or drowsiness is feeling like you have to sleep. If you’re sleepy, you might be able to sleep if given the chance, or you may doze off by accident.
    • You can feel fatigued but have difficulty falling asleep.
    • Although sleepiness and fatigue are different, you can have both at the same time.

  • Flumazenil is a GABA-A receptor antagonist medicine that doctors usually use as an intravenous (IV) treatment for oversedation with benzodiazepine medicines (such as Ambien or Valium). Compounding pharmacists can make flumazenil into a skin cream or lozenge to treat excessive daytime sleepiness (EDS).

    Brand names include Romazicon. To learn more, visit our FAQs about Flumazenil Access.

  • The United States Food and Drug Administration (FDA) is an agency within the U.S. Department of Health and Human Services. It is responsible for protecting the public health by ensuring the safety, effectiveness, quality, and security of human and veterinary drugs, vaccines, and other biologic products and medical devices. The FDA is also responsible for the safety and security of most of our nation’s food supply and of cosmetics.

  • The United States Food and Drug Administration (FDA) is an agency within the U.S. Department of Health and Human Services. It is responsible for protecting the public health by ensuring the safety, effectiveness, quality, and security of human and veterinary drugs, vaccines, and other biologic products and medical devices. The FDA is also responsible for the safety and security of most of our nation’s food supply and of cosmetics.

  • The Functional Outcomes of Sleep Questionnaire (FOSQ) was developed in 1997 as a means to measure the impact of excessive daytime sleepiness on a person’s daily ability to function. The 30 questions are divided into five subscales – activity level, vigilance, intimacy and sexual relationships, general productivity, and social outcomes. A shorter version, FOSQ-10, is also available; this shorter version contains only 10 questions.

  • The Functional Outcomes of Sleep Questionnaire (FOSQ) was developed in 1997 as a means to measure the impact of excessive daytime sleepiness on a person’s daily ability to function. The 30 questions are divided into five subscales – activity level, vigilance, intimacy and sexual relationships, general productivity, and social outcomes. A shorter version, FOSQ-10, is also available; this shorter version contains only 10 questions.

  • g

  • Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in your central nervous system (brain and spinal cord). It blocks or stops chemical messages from being sent to the next nerve cell. This causes nerve cells to have less of an effect. GABA also relaxes your muscles during sleep and sets your overall muscle tone.

    To learn more, visit our “What is GABA?” web page.

  • GABA-related hypersomnia happens in people who have both:

    • A hypersomnia disorder, such as:
      • Idiopathic hypersomnia
      • Narcolepsy type 1 or 2
      • Hypersomnia or narcolepsy associated with another disorder
      • Kleine-Levin syndrome
    • A substance in their cerebrospinal fluid (CSF) that makes the effects of GABA stronger, causing sleepiness. Substances that cause sleepiness are called somnogens.

    To learn more, visit our “What is GABA?” web page.

  • A genome-wide association study (GWAS) is a study that looks at people’s complete genetic material in order to identify DNA markers. It then compares the markers from people with a disease or trait to the markers for people without the disease or trait.

  • A genome-wide association study (GWAS) is a study that looks at people’s complete genetic material in order to identify DNA markers. It then compares the markers from people with a disease or trait to the markers for people without the disease or trait.

  • Your genotype is your complete heritable genetic identity; it is your unique genome that would be revealed by personal genome sequencing. However, the word genotype can also refer just to a particular gene or set of genes carried by an individual.” Read more HERE.

  • h

  • The Hypersomnia Foundation (HF) is a nonprofit 501(c)(3) organization that engages, informs and champions our global community to improve the lives of people with idiopathic hypersomnia and related sleep disorders. Read more about our mission, vision, values, goals and achievements HERE.

  • A high-deductible health plan is an insurance plan with a higher deductible than a traditional health plan. The monthly premium is usually lower, but you pay more health care costs yourself (also called your deductible) before the insurance company starts to pay its share.

  • Hormones are chemicals that help different parts of your body know how they should work.

  • The human leukocyte antigen (HLA) system is the group of genes (a section or part of your DNA that has instructions for making things your body needs to work) that instruct proteins on the surface of white blood cells. These proteins help control your immune system and your ability to fight infection.

    HLA typing is a test that identifies your human leukocyte antigens. Doctors may also order HLA typing to help diagnose narcolepsy type 1 (NT1). Most people with NT1 have the HLA-DQB1*0602 gene and are referred to as being “HLA-DQB1*0602 positive.”

  • The human leukocyte antigen (HLA) system is the group of genes (a section or part of your DNA that has instructions for making things your body needs to work) that instruct proteins on the surface of white blood cells. These proteins help control your immune system and your ability to fight infection.

    HLA typing is a test that identifies your human leukocyte antigens. Doctors may also order HLA typing to help diagnose narcolepsy type 1 (NT1). Most people with NT1 have the HLA-DQB1*0602 gene and are referred to as being “HLA-DQB1*0602 positive.”

  • A humoral substance is a body fluid, or a substance related to a body fluid, especially with regard to immune responses involving antibodies in body fluids (as distinct from cells). Many of the bacteria that cause infectious diseases in humans multiply in the extracellular spaces of the body, and these extracellular spaces are protected by the humoral immune response, in which antibodies produced by B cells cause the destruction of extracellular microorganisms and prevent the spread of intracellular infections.

  • Hypersomnia is a type of sleep disorder that causes people to sleep excessive amounts (long sleep), have excessive daytime sleepiness, or both. Treatments for these disorders are often very similar, and current research shows that there may be significant overlap among some of them.

    Hypersomnias are also called central disorders of hypersomnolence (CDH). They include:

    • Idiopathic hypersomnia
    • Narcolepsy types 1 and 2
    • Kleine-Levin syndrome
    • Hypersomnia and narcolepsy associated with other disorders

    Hypersomnia refers to a type of sleep disorder. Hypersomnolence refers to the specific symptoms of long sleep or excessive daytime sleepiness (EDS). For example:

    • People have or are diagnosed with a hypersomnia (a disorder).
      "My loved one has been diagnosed with a hypersomnia called narcolepsy type 2.”
    • People experience hypersomnolence (a symptom).
      "My loved one has severe, daily hypersomnolence. They're extremely sleepy almost all the time."

    To learn more, visit our web pages:

  • The hypothalamus is a very small part of the brain that has a number of very important functions: it controls the autonomic nervous system and processes and secretes neurohormones. These hormones regulate body temperature, hunger, thirst, sleep, fatigue, sex drive, mood, sleep, alertness, and circadian rhythms.

  • In science, a hypothesis is an idea or explanation that researchers then test in an experiment.

  • i

  • IBCLC is a degree (credential) that stands for International Board Certified Lactation Consultant.

  • Idiopathic hypersomnia (IH) is a long-lasting (chronic) sleep disorder of the brain (neurologic disorder). It affects the brain’s ability to control sleep and wakefulness and causes excessive daytime sleepiness (EDS). Other symptoms may include brain fog, sleep drunkenness (or severe sleep inertia), and long unrefreshing naps. Read more on our IH web page.

    Idiopathic hypersomnia is defined by the International Classification of Sleep Disorders (ICSD). Hypersomnolence disorder is the most similar diagnosis defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM). Read more on our web page for doctors “Diagnosis, classification, symptoms, and causes of hypersomnias.”

  • Idiopathic hypersomnia (IH) is a long-lasting (chronic) sleep disorder of the brain (neurologic disorder). It affects the brain’s ability to control sleep and wakefulness and causes excessive daytime sleepiness (EDS). Other symptoms may include brain fog, sleep drunkenness (or severe sleep inertia), and long unrefreshing naps. Read more on our IH web page.

    Idiopathic hypersomnia is defined by the International Classification of Sleep Disorders (ICSD). Hypersomnolence disorder is the most similar diagnosis defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM). Read more on our web page for doctors “Diagnosis, classification, symptoms, and causes of hypersomnias.”

  • In vitro means that something — for example, an experiment — takes place outside the body in an artificial environment.

  • An infant is a baby 1 year or younger.

  • Inflammation happens when the body's immune system acts to remove infection, injury, or harmful substances and begin the healing process. Long-lasting (chronic) inflammation may happen if the immune system is overstimulated for a long period of time, and this may cause health problems.

  • Insufficient sleep syndrome happens when you regularly don’t have enough time to get as much sleep as you need. This can happen because of your habits or responsibilities. A doctor can test how much sleep you get and the timing of your sleep by having you keep a sleep diary. They may also ask you to wear a special sensor called an actigraph, which measures your physical activity levels. Insufficient sleep syndrome goes away if you start getting as much sleep as you need.

  • An insurance policy is a contract with the insurer. It may be called other names, such as a benefits contract, benefits book, certificate of coverage, or evidence of coverage.

  • The International Classification of Sleep Disorders (ICSD) is a reference book that helps doctors figure out if someone has a sleep disorder. It’s published by the American Academy of Sleep Medicine (AASM) and updated as researchers learn more about sleep disorders. The most recent version is 2023’s ICSD-3-TR (text revision).

    The ICSD-3-TR puts sleep disorders into these groups:

    • Insomnia
    • Sleep-related breathing disorders
    • Central disorders of hypersomnolence (CDH)
    • Circadian rhythm sleep-wake disorders
    • Parasomnias
    • Sleep-related movement disorders
    • Other sleep disorders

    The CDH are also called hypersomnia disorders, or hypersomnias. They include:

    • Idiopathic hypersomnia
    • Narcolepsy types 1 and 2
    • Kleine-Levin syndrome
    • Hypersomnia and narcolepsy associated with other disorders

    To learn more about how doctors figure out if someone has a sleep disorder, see our web page “Diagnosis, classification, symptoms, and causes of hypersomnias.”

  • The International Classification of Sleep Disorders (ICSD) is a reference book that helps doctors figure out if someone has a sleep disorder. It’s published by the American Academy of Sleep Medicine (AASM) and updated as researchers learn more about sleep disorders. The most recent version is 2023’s ICSD-3-TR (text revision).

    The ICSD-3-TR puts sleep disorders into these groups:

    • Insomnia
    • Sleep-related breathing disorders
    • Central disorders of hypersomnolence (CDH)
    • Circadian rhythm sleep-wake disorders
    • Parasomnias
    • Sleep-related movement disorders
    • Other sleep disorders

    The CDH are also called hypersomnia disorders, or hypersomnias. They include:

    • Idiopathic hypersomnia
    • Narcolepsy types 1 and 2
    • Kleine-Levin syndrome
    • Hypersomnia and narcolepsy associated with other disorders

    To learn more about how doctors figure out if someone has a sleep disorder, see our web page “Diagnosis, classification, symptoms, and causes of hypersomnias.”

  • An intrauterine device (IUD) is a form of birth control. It’s a tiny, plastic device that a doctor puts into the uterus to help prevent pregnancy. It can stay in place for up to several years and is one of the birth control methods that works best to prevent pregnancy. The 2 types of IUDs are:

    • Hormonal IUD, which uses a progestin hormone to prevent pregnancy. Because the hormone works directly within the uterus, it doesn’t interact with hypersomnia medicines.
    • Copper IUD, which uses a tiny bit of copper to prevent pregnancy. This is also the most effective way to prevent pregnancy after unprotected sex (emergency contraception) if used within 5 days after sex.

  • An intrauterine device (IUD) is a form of birth control. It’s a tiny, plastic device that a doctor puts into the uterus to help prevent pregnancy. It can stay in place for up to several years and is one of the birth control methods that works best to prevent pregnancy. The 2 types of IUDs are:

    • Hormonal IUD, which uses a progestin hormone to prevent pregnancy. Because the hormone works directly within the uterus, it doesn’t interact with hypersomnia medicines.
    • Copper IUD, which uses a tiny bit of copper to prevent pregnancy. This is also the most effective way to prevent pregnancy after unprotected sex (emergency contraception) if used within 5 days after sex.

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  • Kleine-Levin syndrome (KLS) is a rare hypersomnia sleep disorder of the brain (neurologic disorder). It affects the brain’s ability to control sleep, wakefulness, thinking, and behaviors. KLS causes repeated episodes (periods) of very long sleep (often 16 to 20 hours a day) and excessive daytime sleepiness (EDS).

    Episodes may last for days or weeks at a time. During episodes, people who have KLS have other symptoms, such as:

    • Being slow in thinking and speaking
    • Having memory loss
    • Being exhausted and bedridden, with no motivation for talking, eating, or seeing people (major apathy)
    • Feeling that things are unreal (derealization)
    • Eating much more than they normally do
    • Doing things they wouldn’t usually do

    These symptoms usually go away between episodes. Read more on our KLS web page.

  • Kleine-Levin syndrome (KLS) is a rare hypersomnia sleep disorder of the brain (neurologic disorder). It affects the brain’s ability to control sleep, wakefulness, thinking, and behaviors. KLS causes repeated episodes (periods) of very long sleep (often 16 to 20 hours a day) and excessive daytime sleepiness (EDS).

    Episodes may last for days or weeks at a time. During episodes, people who have KLS have other symptoms, such as:

    • Being slow in thinking and speaking
    • Having memory loss
    • Being exhausted and bedridden, with no motivation for talking, eating, or seeing people (major apathy)
    • Feeling that things are unreal (derealization)
    • Eating much more than they normally do
    • Doing things they wouldn’t usually do

    These symptoms usually go away between episodes. Read more on our KLS web page.

  • A knockout mouse is a mouse in which researchers have inactivated, or "knocked out," an existing gene in the animal by replacing the gene or disrupting it with a different piece of DNA.

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  • A lead compound is a peptide, small molecule, or other agent with pharmacological or biochemical properties, which may have therapeutic potential and value as a starting point for drug development.

  • Levothyroxine is a thyroid medicine that replaces a hormone normally produced by the thyroid gland to regulate the body’s energy and metabolism. Doctors usually use it to treat hypothyroidism (an underactive thyroid gland). Doctors sometimes use it to treat excessive daytime sleepiness (EDS).

    Brand names include Euthyrox, Levo-T, Levothroid, Levoxyl, Synthroid, Thyquidity, Tirosint, and Unithroid.

  • Liquid chromatography-mass spectrometry (LC-MS) is a chemical analysis technique used to separate, identify, measure, and analyze substances in a mixture. It combines the physical separation capabilities of liquid chromatography with the mass analysis capabilities of mass spectrometry. (While liquid chromatography separates the individual components of a mixture, mass spectrometry ionizes atoms or molecules to facilitate their separation and detection in accordance with their molecular masses and charges.) This tandem technique is used in a variety of fields, including biotechnology, pharmaceutical research and food processing, especially when the mixture is highly complex.

  • Liquid chromatography-mass spectrometry (LC-MS) is a chemical analysis technique used to separate, identify, measure, and analyze substances in a mixture. It combines the physical separation capabilities of liquid chromatography with the mass analysis capabilities of mass spectrometry. (While liquid chromatography separates the individual components of a mixture, mass spectrometry ionizes atoms or molecules to facilitate their separation and detection in accordance with their molecular masses and charges.) This tandem technique is used in a variety of fields, including biotechnology, pharmaceutical research and food processing, especially when the mixture is highly complex.

  • Long sleep is the need to sleep either:

    • More than 9 hours at night (or whenever you sleep the longest)
    • At least 11 hours in a 24-hour period (including naps)

  • In a longitudinal study, researchers observe the same subjects and repeatedly gather data, or information, over a period of time.

  • A lumbar puncture (LP), also called a spinal tap, is a medical test to collect cerebrospinal fluid (CSF) from your spinal canal to send to a lab for testing.

  • A lumbar puncture (LP), also called a spinal tap, is a medical test to collect cerebrospinal fluid (CSF) from your spinal canal to send to a lab for testing.

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  • The Hypersomnia Foundation’s Medical Advisory Board. Read more HERE.

  • MRI (magnetic resonance imaging) uses strong magnets and radio waves housed inside a specialized machine or scanner to make detailed 3-D pictures or images of organs and tissues within the body.

  • MRI (magnetic resonance imaging) uses strong magnets and radio waves housed inside a specialized machine or scanner to make detailed 3-D pictures or images of organs and tissues within the body.

  • The Maintenance of Wakefulness Test (MWT) is a sleep study (polysomnography) that measures your likelihood of falling asleep when you’re trying to stay awake during the day. You recline in bed in a dark, quiet, comfortable room and try to stay awake during 4 measurement sessions that start at about 9 or 10 a.m. and last 40 minutes each.

    If you fall asleep, you’re only allowed to sleep for 90 seconds. A sleep tech will then wake you up and keep you awake until the next measurement session. If you don’t fall asleep within 40 minutes, that measurement session ends. The measurement sessions are usually every 2 hours. Most people without sleep problems are able to stay awake for at least the first 8 minutes of each measurement session.

  • The Maintenance of Wakefulness Test (MWT) is a sleep study (polysomnography) that measures your likelihood of falling asleep when you’re trying to stay awake during the day. You recline in bed in a dark, quiet, comfortable room and try to stay awake during 4 measurement sessions that start at about 9 or 10 a.m. and last 40 minutes each.

    If you fall asleep, you’re only allowed to sleep for 90 seconds. A sleep tech will then wake you up and keep you awake until the next measurement session. If you don’t fall asleep within 40 minutes, that measurement session ends. The measurement sessions are usually every 2 hours. Most people without sleep problems are able to stay awake for at least the first 8 minutes of each measurement session.

  • Major apathy is:

    • The complete lack of motivation to do usually pleasurable things like talking with other people, using your smartphone or social media, bathing, or caring about what's going on around you
    • Having mostly negative emotions and finding it hard to feel or express positive emotions

  • Mazindol is a stimulant medicine. It raises alertness like amphetamines, but it has little or no effect on mood or the cardiovascular system. Researchers are studying it as a treatment for excessive daytime sleepiness (EDS) and cataplexy.

    Brand names include Quilience.

  • Meditation is a practice that helps you become a nonjudgmental observer of your own mind. It helps you train your brain to notice your thoughts and let go of the unhelpful ones.

  • Melatonin is a hormone your body makes to help you sleep. It tells your body when it’s time to go to sleep and when it’s time to wake up. You make more melatonin when it’s dark outside and less when it’s light. You also make less melatonin as you get older. Doctors may recommend slow-release melatonin supplements to treat excessive daytime sleepiness (EDS) and severe sleep inertia.

  • Messenger RNA (mRNA) is a subtype of RNA. An mRNA molecule is created during transcription to carry a portion of the DNA code (genetic information) to the ribosome (the site in the cell where proteins are made).

  • Messenger RNA (mRNA) is a subtype of RNA. An mRNA molecule is created during transcription to carry a portion of the DNA code (genetic information) to the ribosome (the site in the cell where proteins are made).

  • A metabolite is any substance produced during digestion or other chemical processes that occur in the body. Metabolite may also refer to the product that remains after a drug is broken down by the body.

  • Mindfulness is the practice of bringing all of your attention to the present moment.

  • Modafinil and armodafinil are stimulant medicines doctors use to treat excessive daytime sleepiness (EDS).

    Modafinil brand names include Alertec, Modalert, Modavigil, and Provigil.

    Armodafinil brand names include Acronite, Armod, Armoda, Artivil, Modavital, Neoresotyl, Nuvigil, R-Modawake, and Waklert.

  • Motor hyperactivity includes talking more than you usually do or being more physically active than usual for you. This symptom often happens when people who have hypersomnias are fighting sleepiness and trying to stay alert.

  • The Multiple Sleep Latency Test (MSLT) is a sleep study (polysomnography) that measures how quickly you fall asleep in a quiet environment during the day. The MSLT typically consists of 4 or 5 scheduled nap sessions, separated by 2-hour breaks.

    During each nap session, you lie in bed in a dark, quiet room and try to go to sleep. The time that it takes you to fall asleep is called the sleep latency. You‘ll be allowed to sleep for a maximum of 15 minutes during each session. You’ll be awakened if you don’t wake up on your own. If you don’t fall asleep within 20 minutes, the nap session will end.

  • The Multiple Sleep Latency Test (MSLT) is a sleep study (polysomnography) that measures how quickly you fall asleep in a quiet environment during the day. The MSLT typically consists of 4 or 5 scheduled nap sessions, separated by 2-hour breaks.

    During each nap session, you lie in bed in a dark, quiet room and try to go to sleep. The time that it takes you to fall asleep is called the sleep latency. You‘ll be allowed to sleep for a maximum of 15 minutes during each session. You’ll be awakened if you don’t wake up on your own. If you don’t fall asleep within 20 minutes, the nap session will end.

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  • People who have hypersomnias often need naps, which are hard or impossible to avoid.

    • In idiopathic hypersomnia, naps are usually long (more than 1 hour), unrefreshing (non-restorative), and may make people feel even worse
    • In narcolepsy type 2, naps are usually short and somewhat refreshing (restorative)
    • In narcolepsy type 1, naps are usually short and refreshing

  • Narcolepsy is a long-lasting (chronic) hypersomnia sleep disorder of the brain (neurologic disorder). It affects the brain’s ability to control sleep and wakefulness. There are 2 types of narcolepsy:

    • Narcolepsy type 1 (NT1) with cataplexy or low orexin levels
    • Narcolepsy type 2 (NT2) without cataplexy

    The most common symptoms of NT1 are:

    • Excessive daytime sleepiness (EDS)
    • Cataplexy
    • Disrupted nighttime sleep
    • Needed naps
    • Sleep-related hallucinations
    • Sleep paralysis
    • Brain fog

    NT2 symptoms may include any of the NT1 symptoms except cataplexy. NT2 symptoms may also overlap with symptoms of idiopathic hypersomnia, such as severe sleep inertia and long sleep.

    Read more on our web pages:

  • If you look at a human or mammal’s brain from the top or the sides, what you see is the neocortex. In humans, this part of the brain, which is about 2-4 mm thick (a thickness somewhere between the size of the point of a crayon and the eraser end of a pencil), forms ridges or deep grooves called sulci. The neocortex in humans controls sensory perception, generation of motor commands, spatial reasoning, conscious thought, and language.

  • Neuroendocrine means both neural and endocrine in structure and function. Neuroendocrine cells are like nerve cells (neurons), but they also make hormones, like cells of the endocrine system (endocrine cells) do. Neuroendocrine cells receive neuronal input (neurotransmitters released by nerve cells) and, as a result of this input, release hormones into the bloodstream.

  • Neurologic means of the brain or nervous system (the spinal cord and nerves).

  • A neuromodulator is a chemical substance released from a neuron in the central nervous system (the brain or spinal cord), or in the periphery, that transmits information to other neurons, altering their activities. A neuromodulator affects not just a single cell, but groups of neurons or effector cells that have the appropriate receptors. Unlike a neurotransmitter, it may be released at sites other than synaptic sites, it often acts through second messengers, and it can produce long-lasting effects. The release may be local, so that only nearby neurons or effectors are influenced, or it may be more widespread.

  • Neurons (nerve cells) are specialized cells in your nervous system that send information to other nerve cells, muscle cells, or gland cells.

  • A neurotransmitter is a chemical messenger in your body. It carries messages from a nerve cell to other nerve cells, muscles, organs, glands, and more. These messages help you:

    • Move your body
    • Feel sensations
    • Keep your heart beating
    • Take in and respond to all the information your body gets from itself and your environment

    There are many different types of neurotransmitters in your body, such as:

    • Dopamine — plays a role in your movement, attention, emotions, and motivation
    • GABA — stops or blocks chemical messages from nerve cells
    • Histamine — plays a role in your reticular activating system (the part of your brain that wakes you up), your body’s immune response, and your gut (stomach and intestines) function
      • Doctors may use histamine to tell if a person has problems in their hypothalamus (a part of your brain)
    • Norepinephrine — plays a role in your “flight-or-fight” response (getting your brain and body ready for action), increasing your focus, alertness, and ability to access your memories
    • Orexin — plays a role in your sleep-wake control, how awake you feel during the day, appetite, energy, and mood

    Some neurotransmitters, like GABA, block or stop chemical messages from being sent to the next nerve cell. These are called inhibitory neurotransmitters.

  • A non-cataplectic hypersomnia is one without cataplexy. This includes narcolepsy type 2, idiopathic hypersomnia, KLS, and hypersomnias due to certain medical conditions.

  • NDRI (norepinephrine-dopamine reuptake inhibitor) medicines include:

    • Methylphenidate, which is a stimulant doctors can use to treat excessive daytime sleepiness (EDS) and severe sleep inertia.
      • Brand names include Adhansia XR, Aptensio XR, Concerta, Cotempla XR-ODT, Daytrana, Focalin, Jornay PM, Metadate CD, Metadate ER, Methylin, Methylin ER, QuilliChew ER, Quillivant XR, Ritalin, Ritalin LA, and Ritalin SR.
    • Solriamfetol, which is a stimulant doctors can use to treat EDS.
      • Brand names include Sunosi.
    • Bupropion, which doctors usually use as an antidepressant. It has wake-promoting effects, and doctors may use it to also treat excessive daytime sleepiness (EDS) and severe sleep inertia.
      • Brand names include Aplenzin, Budeprion SR, Budeprion XL, Buproban, Forfivo, Forfivo XL, Wellbutrin, Wellbutrin SR, Wellbutrin XL, and Zyban.

  • NDRI (norepinephrine-dopamine reuptake inhibitor) medicines include:

    • Methylphenidate, which is a stimulant doctors can use to treat excessive daytime sleepiness (EDS) and severe sleep inertia.
      • Brand names include Adhansia XR, Aptensio XR, Concerta, Cotempla XR-ODT, Daytrana, Focalin, Jornay PM, Metadate CD, Metadate ER, Methylin, Methylin ER, QuilliChew ER, Quillivant XR, Ritalin, Ritalin LA, and Ritalin SR.
    • Solriamfetol, which is a stimulant doctors can use to treat EDS.
      • Brand names include Sunosi.
    • Bupropion, which doctors usually use as an antidepressant. It has wake-promoting effects, and doctors may use it to also treat excessive daytime sleepiness (EDS) and severe sleep inertia.
      • Brand names include Aplenzin, Budeprion SR, Budeprion XL, Buproban, Forfivo, Forfivo XL, Wellbutrin, Wellbutrin SR, Wellbutrin XL, and Zyban.

  • NRI (norepinephrine reuptake inhibitor) medicines are non-stimulant antidepressants. Doctors can use them to treat excessive daytime sleepiness (EDS) and cataplexy.

    NRIs include:

    • Atomoxetine (such as Attera, Attentin, Axepta, Axetra, Stramox, Strattera, and Tomoxetin)
    • Reboxetine (such as Davedex, Edronax, Irenor, Norebox, Prolift, Solvex, Yeluoshu, and Zuolexin)

    These are sometimes called selective NRIs, but they aren’t SNRIs (serotonin and norepinephrine reuptake inhibitors).

  • NRI (norepinephrine reuptake inhibitor) medicines are non-stimulant antidepressants. Doctors can use them to treat excessive daytime sleepiness (EDS) and cataplexy.

    NRIs include:

    • Atomoxetine (such as Attera, Attentin, Axepta, Axetra, Stramox, Strattera, and Tomoxetin)
    • Reboxetine (such as Davedex, Edronax, Irenor, Norebox, Prolift, Solvex, Yeluoshu, and Zuolexin)

    These are sometimes called selective NRIs, but they aren’t SNRIs (serotonin and norepinephrine reuptake inhibitors).

  • A nucleotide is one of the structural components, or building blocks, of DNA and RNA. A nucleotide consists of one of four chemicals (adenine, thymine, guanine or cytosine), plus a molecule of sugar and a molecule of phosphoric acid.

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  • Obstructive sleep apnea (OSA) is a sleep disorder characterized by repetitive partial and/or complete collapses of the upper airway, associated with arousals/awakenings and/or decreases in oxygen levels in the blood. The episodes last more than 10 seconds, by definition, but can last up to 30-60 seconds. Untreated sleep apnea may cause daytime sleepiness and increased risk of cardiovascular events, such as high blood pressure, heart attack and stroke.

  • Obstructive sleep apnea (OSA) is a sleep disorder characterized by repetitive partial and/or complete collapses of the upper airway, associated with arousals/awakenings and/or decreases in oxygen levels in the blood. The episodes last more than 10 seconds, by definition, but can last up to 30-60 seconds. Untreated sleep apnea may cause daytime sleepiness and increased risk of cardiovascular events, such as high blood pressure, heart attack and stroke.

  • Off-label means a doctor prescribes a medicine that’s FDA-approved for other health conditions but not for your diagnosis.

  • Opioids are substances that doctors may prescribe as medicine to treat severe pain.

  • Orexin is a neurotransmitter (chemical messenger) that plays a role in your:

    • Sleep-wake regulation (control)
    • Feeling awake during the daytime
    • Appetite
    • Energy levels
    • Reward systems
    • Thinking
    • Mood

    People who have narcolepsy type 1 have low orexin in their cerebrospinal fluid (CSF). Orexin is also called hypocretin.

  • Organogenesis is the production and development (genesis) of the organs of an animal or plant.

  • Orphan Drug Designation (ODD) in the U.S. means that a drug has been designated by the U.S. FDA as an "orphan drug" pursuant to the Orphan Drug Act of 1983. This law was passed to facilitate the development of drugs for rare diseases that affect small numbers of people living in the U.S. (which is defined as affecting less than 200,000 people in the U.S.). Orphan drug designation does not mean that the drug is safe or effective, and does not mean that it is legal to market or sell the drug in the U.S. Rather, the designation means only that the drug's sponsor qualifies for certain benefits from the U.S. government, including tax incentives and market exclusivity for 7 years. Orphan drugs normally follow the same regulatory approval process as other drugs (including dosing, safety and efficacy). However, some statistical requirements are lessened (such as not requiring the same number of patients in a Phase III clinical trial as would be required for a non-orphan drug), in order to try to provide a more streamlined process for gaining ultimate approval. Japan adopted a similar law in 1993; the European Union adopted a similar law in 2000.

  • Orthostatic intolerance is when you’re unable to stay standing up without having symptoms such as:

    • Heart palpitations (feeling that your heart is beating too hard, too fast, or skipping beats)
    • Low blood pressure
    • Feeling dizzy
    • Weakness
    • Passing out
    • Nausea (upset stomach)
    • Blurry vision

  • Oxidation is the chemical process by which oxygen combines with an element, causing the element to undergo a change. Specifically, oxidation is the loss of electrons – it occurs whenever an element is combined with oxygen, thereby giving away electrons. [Common examples of oxidation are (1) when iron reacts with oxygen, and changes the iron to rust, and (2) when cut fruit is exposed to oxygen and turns brown.)] Sleep researchers have examined whether people with narcolepsy symptoms might have reduced oxidation of their fatty acids, which are vital for cellular energy. Some of these researchers have advocated for L-carnitine supplementation in order to increase this fatty acid oxidation in people with narcolepsy.

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  • The PAAC is the Hypersomnia Foundation's Patient Advisory and Advocacy Council (PAAC). This council consists of patient and supporter volunteers who meet monthly by phone conference to offer feedback to HF and share the needs of the hypersomnia community. They play a very valuable role for HF and the hypersomnia community at large.

    Interested in joining the PAAC? It requires commitment to a monthly conference call, with possible email correspondence in-between. Members have IH or a related sleep disorder, or have a loved one with one of these rare disorders. The group is small so that all members can join in the discussion, and members typically rotate after a period of time. If you are interested in volunteering, please send an email to info@​hypersomniafoundation.org with the subject line “PAAC.”

  • Periprocedural means happening soon before, during, or soon after having a medical procedure, such as a surgery.

  • Pharmacokinetics is the study of how drugs/pharmaceuticals are processed by the body (how they move through the body, hence "kinetics").

  • A phenotype is a physical appearance, such as height, or a biochemical characteristic, such as blood type, of an organism. Most phenotypes are influenced by both genotype and the environment. Read more HERE.

  • Pitolisant is a non-stimulant wake-promoting medicine that works by raising histamine levels. Doctors use it to treat excessive daytime sleepiness (EDS) and cataplexy.

    Brand names include Wakix.

  • A placebo is an inactive (or sham) substance that is designed to look like the substance or drug that is being studied. A placebo is used as a control in clinical trials and does not contain any active materials.

  • A placebo-controlled trial or study is one in which the effect of a drug is compared with the effect of a placebo. In placebo-controlled trials, participants receive either the drug being studied or a placebo. The results of the drug group and the placebo group are then compared to see if the drug is more effective in treating the condition than is the placebo.

  • A positron emission tomography (PET) scan creates computerized images of chemical changes that take place in tissue. In this test, various radioactive materials (tracers) and substances are injected into patients’ veins. The patient is then scanned in a special machine or scanner. Radiologists can then identify activity in certain parts of the brain by measuring blood flow and oxygen and glucose metabolism in the tissues of the working brain.

  • Postural orthostatic tachycardia syndrome (POTS), also known as postural tachycardia syndrome, is a disorder of the autonomic nervous system characterized by an excessive increase in heart rate upon standing.

  • Postural orthostatic tachycardia syndrome (POTS), also known as postural tachycardia syndrome, is a disorder of the autonomic nervous system characterized by an excessive increase in heart rate upon standing.

  • Prior authorization is a requirement for a doctor or other healthcare professional to get approval from your insurer before prescribing medicine or doing a health procedure for you. This method of controlling costs is also called pre-approval, precertification, or predetermination.

  • Prudent means acting with or showing care and thought for the future.

  • The Psychomotor Vigilance Task (PVT) is a tool used to measure sustained attention and alertness. It measures the speed with which subjects respond to a visual stimulus. In the most common PVT tasks, an individual must press a button in response to a light appearing randomly on a handheld device.

  • The Psychomotor Vigilance Task (PVT) is a tool used to measure sustained attention and alertness. It measures the speed with which subjects respond to a visual stimulus. In the most common PVT tasks, an individual must press a button in response to a light appearing randomly on a handheld device.

  • PWH is an acronym for people with hypersomnias. Hypersomnia Foundation uses this term to refer to people with:

    • Idiopathic hypersomnia
    • Narcolepsy type 1 or 2
    • Kleine-Levin syndrome
    • Hypersomnia and narcolepsy associated with other disorders

    PWH is a broader and more inclusive term than PWN (people with narcolepsy) or PWIH (people with idiopathic hypersomnia).

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  • In a randomized controlled clinical trial, participants or subjects are assigned randomly (i.e., by chance) to separate groups that receive different treatments or other interventions. Using chance to divide people into groups means that the groups will be similar and that the effects of the treatments they receive can be compared more fairly.

  • Relative risk is used to compare risk in two different groups of people. Many reports in the media present risk results as relative risk reductions rather than absolute risk reductions. This often makes treatments seem better than they actually are. Similarly, presenting relative risk increases of side effects/negative effects can make them seem worse than they are. Absolute risk is your actual risk over a time period. Read more HERE.

  • Research studies include clinical studies, which include clinical trials and observational clinical studies (with human participants). However, research studies may also involve animals, basic research at the cellular level, or other types of research that do not involve the testing of treatments or other interventions in people. New treatments are first tested in animals or in other ways before being tried in humans. Read more HERE.

  • Restless legs syndrome (RLS) is a sleep disorder of the brain — a neurologic disorder. It causes an overpowering urge to move your body, especially your legs. This happens along with other sensations described as pulling, creeping, tugging, throbbing, itching, aching, burning, or crawling. Symptoms are usually worse when you’re resting or trying to sleep.

  • Restless legs syndrome (RLS) is a sleep disorder of the brain — a neurologic disorder. It causes an overpowering urge to move your body, especially your legs. This happens along with other sensations described as pulling, creeping, tugging, throbbing, itching, aching, burning, or crawling. Symptoms are usually worse when you’re resting or trying to sleep.

  • A ribosome is a minute particle that is present in large numbers in all living cells. It serves as the site in the cell where proteins are made.

  • Ritanserin is a serotonin receptor antagonist that’s been shown in humans to raise deep slow-wave sleep and to improve symptoms in a variety of psychiatric disorders, including OCD, acute mania, and schizophrenia. However, it’s not currently available anywhere in the world. In a 2003 study of 134 people with narcolepsy, adding ritanserin to their usual narcolepsy treatment resulted in a significant rise in nocturnal (nighttime) slow-wave deep sleep and significantly lowered non-REM stage 1 percentage during daytime sleep.

  • s

  • The Hypersomnia Foundation’s Scientific Advisory Board. Read more HERE.

  • SSRIs (selective serotonin reuptake inhibitors) are medicines that raise serotonin levels in the brain. Doctors usually use them to treat depression and anxiety disorders. Doctors may also use them to treat cataplexy.

    SSRIs include:

    • Citalopram (such as Celexa)
      • Escitalopram (such as Lexapro)
    • Fluoxetine (such as Prozac and Sarafem)
    • Paroxetine (such as Brisdelle, Paxil, and Pexeva)
    • Sertraline (such as Zoloft)

  • SSRIs (selective serotonin reuptake inhibitors) are medicines that raise serotonin levels in the brain. Doctors usually use them to treat depression and anxiety disorders. Doctors may also use them to treat cataplexy.

    SSRIs include:

    • Citalopram (such as Celexa)
      • Escitalopram (such as Lexapro)
    • Fluoxetine (such as Prozac and Sarafem)
    • Paroxetine (such as Brisdelle, Paxil, and Pexeva)
    • Sertraline (such as Zoloft)

  • Selegiline is a monoamine oxidase type B (MAO-B) inhibitor medicine that raises dopamine levels in the brain. Doctors may use it to treat excessive daytime sleepiness (EDS).

    Brand names include Eldepryl, Emsam, and Zelapar.

  • The sensitivity of a diagnostic test indicates how often the test will be positive if a person truly has the disease (true positive rate). In other words, if the test is highly sensitive and the test result is negative, you can be nearly certain that the person doesn’t have the disease for which they’re being tested. A sensitive test helps rule out disease (when the result is negative). Read more HERE.

  • SNRIs (serotonin-norepinephrine reuptake inhibitors) are medicines doctors usually use to treat depression, anxiety, and long-term pain (especially nerve pain). Doctors may also use these to treat cataplexy.

    SNRIs include:

    • Duloxetine (such as Cymbalta, Drizalma Sprinkle, and Irenka)
    • Milnacipran (such as Savella)
      • Levomilnacipran (such as Fetzima)
    • Venlafaxine (such as Effexor and Effexor XR)
      • Desvenlafaxine (such as Khedezla and Pristiq)

  • SNRIs (serotonin-norepinephrine reuptake inhibitors) are medicines doctors usually use to treat depression, anxiety, and long-term pain (especially nerve pain). Doctors may also use these to treat cataplexy.

    SNRIs include:

    • Duloxetine (such as Cymbalta, Drizalma Sprinkle, and Irenka)
    • Milnacipran (such as Savella)
      • Levomilnacipran (such as Fetzima)
    • Venlafaxine (such as Effexor and Effexor XR)
      • Desvenlafaxine (such as Khedezla and Pristiq)

  • The SF-36 (or Short-Form Health Survey) is a questionnaire developed by RAND as a part of the Medical Outcomes Study to explain variations in patient outcomes. It is a 36-item, patient-reported survey of generic, coherent, and easily administered quality-of-life questions. The SF-36 is made up of eight scales that are summed to reach the total score. These scales include vitality, physical functioning, bodily pain, general health perceptions, physical role functioning, emotional role functioning, social role functioning, and mental health. The SF-36 does not include a scale to assess sleep.

  • The SF-36 (or Short-Form Health Survey) is a questionnaire developed by RAND as a part of the Medical Outcomes Study to explain variations in patient outcomes. It is a 36-item, patient-reported survey of generic, coherent, and easily administered quality-of-life questions. The SF-36 is made up of eight scales that are summed to reach the total score. These scales include vitality, physical functioning, bodily pain, general health perceptions, physical role functioning, emotional role functioning, social role functioning, and mental health. The SF-36 does not include a scale to assess sleep.

  • A single nucleotide polymorphism (SNP) is a DNA variation in which one nucleotide (the building block of DNA) differs from what is generally observed in the population. SNPs occur normally throughout a person’s DNA — usually about once in every 300 nucleotides. These variations are typically found in the DNA between genes. They can act as markers, helping scientists locate genes that are associated with a specific disease. When SNPs appear within a gene or in a regulatory region near a gene, they may play a more direct role in disease by affecting the function of a gene.

  • A single nucleotide polymorphism (SNP) is a DNA variation in which one nucleotide (the building block of DNA) differs from what is generally observed in the population. SNPs occur normally throughout a person’s DNA — usually about once in every 300 nucleotides. These variations are typically found in the DNA between genes. They can act as markers, helping scientists locate genes that are associated with a specific disease. When SNPs appear within a gene or in a regulatory region near a gene, they may play a more direct role in disease by affecting the function of a gene.

  • Single-photon emission computed tomography (SPECT) is similar to positron emission tomography (PET) in that it uses a radioactive substance (tracer) and a special camera to create 3-D pictures of an internal organ of the body. Like PET, SPECT is particularly useful for looking at blood flow to an organ, such as the heart or brain. The primary difference between the two tests is that the tracers used in SPECT last longer than those used in PET, allowing for a longer time to view the organ at work.

  • Single-photon emission computed tomography (SPECT) is similar to positron emission tomography (PET) in that it uses a radioactive substance (tracer) and a special camera to create 3-D pictures of an internal organ of the body. Like PET, SPECT is particularly useful for looking at blood flow to an organ, such as the heart or brain. The primary difference between the two tests is that the tracers used in SPECT last longer than those used in PET, allowing for a longer time to view the organ at work.

  • Sleep attacks are episodes when you fall asleep in places or at times you don’t want to.

  • A sleep diary is a record of your sleep patterns over a long period of time (usually at least 2 weeks). It includes the time you go to sleep and wake up. A sleep diary can help doctors diagnose sleep disorders.

    A sleep-wake diary (or journal) tracks more data than a sleep diary and can help you see patterns, such as:

    • How your energy and alertness change during the day and
    • What may be making your symptoms better or worse

    To learn more:

  • Sleep efficiency is the percentage of time spent asleep while in bed. It is calculated by dividing the amount of time spent asleep (in minutes) by the total amount of time in bed (in minutes). A normal sleep efficiency is considered to be 85% or higher.

  • Sleep hygiene refers to avoiding lifestyle habits and environmental factors that are counterproductive for sleep. For more information, visit “What does sleep hygiene mean for PWH?” on our Quality of life tips web page.

  • Sleep inertia is when you feel groggy after waking up suddenly, such as when your alarm wakes you up. Symptoms include:

    • Wanting to go back to sleep
    • Being less alert
    • Poor mood
    • Slower reaction time
    • Poorer short-term memory
    • Taking longer to think, reason, remember, and learn

    Sleep inertia usually lasts 15 to 30 minutes, with the symptoms slowly fading over time. It can happen after you’ve been asleep for 30 minutes or longer.

    People with idiopathic hypersomnia often have severe sleep inertia, which is sometimes called sleep drunkenness. Their symptoms can last up to a few hours and can include automatic behaviors. People with severe sleep inertia may be very difficult to wake and may need multiple loud alarms.

  • Sleep onset REM periods (SOREMPs) are REM (rapid eye movement) sleep periods that happen within 15 minutes of falling asleep. If you have SOREMPs, it may mean you have narcolepsy.

  • Sleep onset REM periods (SOREMPs) are REM (rapid eye movement) sleep periods that happen within 15 minutes of falling asleep. If you have SOREMPs, it may mean you have narcolepsy.

  • Sleep paralysis is when you can’t move your body or speak while you’re falling asleep or waking up. It can last from a few seconds to several minutes.

  • Sleep-related hallucinations (or sleep hallucinations) are seeing, hearing, feeling, or smelling something that isn’t actually there while you’re falling asleep or waking up.

    Doctors may call these:

    • Hypnagogic hallucinations (when you’re falling asleep)
    • Hypnopompic hallucinations (when you’re waking up)

  • Sleep is made up of 4 stages:

    • Stage 1 — The lightest stage of sleep
    • Stage 2
    • Stage 3 — The deepest stage of sleep (slow wave sleep)
    • REM (rapid eye movement) – Also called dream sleep
      • During this stage, you have dreams and rapid eye movements, and you can’t move
      • Your breathing and heart rate are less regular than they are in Stages 1 to 3

    Stages 1, 2, and 3 are also called non-rapid eye movement (NREM) sleep.

    In your first sleep cycle: As you fall asleep, you go from stage 1 to stage 2, then to stage 3. Sometimes you may go back and forth between stages 2 and 3. After that, you go into REM sleep.

    While you sleep, you go through several cycles of all 4 stages. A typical sleep cycle lasts about 90 to 110 minutes. During later sleep cycles, your Stage 3 sleep happens earlier in the cycle and you have more REM sleep. For example, the REM stage in your first sleep cycle usually lasts about 10 minutes. Each later REM stage gets longer, with the final REM stage lasting up to an hour.

    Usually, about 25% (one quarter) of your time asleep is REM. The other 75% (three quarters) is NREM.

  • A sleep study, also called polysomnography (PSG), is a test used to diagnose sleep disorders.

    During this test, several devices will be attached to you while you sleep to record information, such as:

    • Brain waves
    • Eye movements
    • Muscle tone in your chin
    • The amount of oxygen in your blood
    • Heart rate
    • Breathing rate
    • Airflow (how much air is going in and out of your body)
    • Respiratory effort (how easy it is to breathe)
    • Sounds you make (such as snoring)
    • Movements from your arms and legs

    This information allows doctors to determine your sleep stages and other data that can help diagnose sleep disorders.

    There are several types of sleep studies, including:

  • Sleepiness or drowsiness is feeling like you have to sleep. If you’re sleepy, you might be able to sleep if given the chance, or you may doze off by accident.

    Sleepiness is different from fatigue:

    • Fatigue is a lack of physical or mental energy. It’s when you feel tired or exhausted.
    • You can feel fatigued but have difficulty falling asleep.
    • Although sleepiness and fatigue are different, you can have both at the same time.

  • Oxybates are GABA-B receptor agonist medicines. Doctors use them to treat excessive daytime sleepiness (EDS), severe sleep inertia, sleep disruption, and cataplexy.

    Oxybates include:

    • Sodium oxybate (such as Alcover, Gamma-OH, Natrii oxybutyras Kalceks, Somsanit, and Xyrem)
    • Lower-sodium oxybate (such as Xywav)
    • Extended release sodium oxybate (such as Lumryz)

  • A somnogen is any substance that causes sleepiness.

  • The specificity of a diagnostic test indicates how often the test will be negative if a person does not have the disease (true negative rate). In other words, if the test result for a highly specific test is positive, you can be nearly certain that the person actually has the disease for which they’re being tested. A very specific test rules in disease with a high degree of confidence. Read more HERE.

  • The striatum is a section of the brain that lies beneath the front part of the cortex. This area of the brain has a number of functions, including planning and executing movement and controlling the reward system. The striatum looks as if it has grey and white stripes, and thus the name striae or stripe.

  • A susceptibility gene is a permanent change in a gene (mutation) that increases a person’s susceptibility to or likelihood of developing a certain disease or disorder. When such a mutation is passed from a biological parent to a child, symptoms of the disease or disorder are more likely to occur, but it is not certain that the symptoms will occur.

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  • Teratogenic refers to a substance that is capable of interfering with the development of a fetus, causing birth defects.

  • A tilt table test is typically performed in individuals with significant fainting spells and/or dizziness of unknown cause. The test monitors an individual’s heart rate, blood pressure, and symptoms while lying flat on a table and then standing upright for a defined period of time. Diagnoses rendered after a tilt table test may include orthostatic hypotension, reflex syncope, and postural orthostatic tachycardia syndrome (POTS).

  • Transcription is the process in which RNA is made from DNA. In transcription, the DNA sequence of a gene is transcribed (copied) to make an RNA molecule.

  • TCAs (tricyclic antidepressants) are medicines doctors usually use to treat depression. Doctors may also use them to treat cataplexy.

    TCAs include:

    • Clomipramine (such as Anafranil)
    • Protriptyline (such as Vivactil), which has wake-promoting effects, so doctors can use it to also treat excessive daytime sleepiness (EDS)

  • TCAs (tricyclic antidepressants) are medicines doctors usually use to treat depression. Doctors may also use them to treat cataplexy.

    TCAs include:

    • Clomipramine (such as Anafranil)
    • Protriptyline (such as Vivactil), which has wake-promoting effects, so doctors can use it to also treat excessive daytime sleepiness (EDS)

  • u

  • Unrefreshing sleep (or non-restorative sleep) is bad quality sleep that doesn’t help you feel rested and refreshed. You wake up feeling like you haven’t slept.

    Refreshing (or restorative) sleep is the opposite. It's normal good quality sleep that helps you feel rested and refreshed.

  • v

  • A birth control ring is a small, flexible ring with estrogen and progestin hormones that you put in your vagina each month to help prevent pregnancy. The hormones work throughout your whole body, not just your uterus, so they do interact with hypersomnia medicines.

  • Vigilance refers to the state of being alert and attentive.