Newly published initial data details differences between IH and narcolepsy.

By Yoona Ha

For some patients with idiopathic hypersomnia, the first signs that something is wrong are a herculean struggle to wake in the morning and a relentless, overwhelming sleepiness throughout the day. They also quickly discover that naps are unrefreshing—they feel just as sleepy upon awakening as they did before they lay down to rest. They feel desperately sleep-deprived, yet they are usually sleeping the recommended number of hours at night.

What makes matters especially challenging for patients who are experiencing excessive daytime sleepiness is the murky diagnosis criteria for idiopathic hypersomnia (sometimes called just “IH”). This is due to the lack of clear biological markers and ambiguous diagnostic criteria. Doctors knew little about what patients with idiopathic hypersomnia were experiencing until recently, when researchers released an analysis of the Hypersomnia Foundation’s International Patient Registry at CoRDS (Coordination of Rare Diseases at Sanford).1

The patient registry was begun in March 2015 for people with idiopathic hypersomnia and other related sleep disorders such as narcolepsy and Kleine-Levin syndrome. Patients self-enroll and complete an in-depth questionnaire on their symptoms, diagnosis, and treatment. Michael Twery, PhD, director of the National Center on Sleep Disorders Research at the National Institutes of Health, was a catalyst for developing this patient-powered registry.

As of September 2020, 2,300 patients—and counting—have enrolled. The goal of the registry is to make available patient data to researchers who are investigating causes and treatments of IH, according to Stephanie Wells, executive director of the Hypersomnia Foundation. Participation in the registry is free and use of the de-identified data for research purposes is also free to qualified investigators.

“Based on registry information alone, we can evaluate clinical treatments in a real-life setting, look at trends in healthcare for rare diseases [like IH], and understand the real-life impact and long-term course of this rare disease,” said Lynn Marie Trotti, MD, MSc, chair of the Hypersomnia Foundation’s medical advisory board, during a presentation on the CoRDS registry at the Hypersomnia Foundation’s conference in 2016. Trotti, an associate professor of neurology at Emory University in Atlanta, has accessed the registry’s data to conduct her own research on IH.

It is not known how prevalent idiopathic hypersomnia is among people in the United States. But it’s estimated that IH is 10 times less frequent than narcolepsy.2 In addition to the problems that patients face in obtaining a correct diagnosis, patients who finally get a diagnosis then face barriers to receiving proper care due to the lack of any medications expressly indicated to treat idiopathic hypersomnia by the US Food and Drug Administration (FDA).

Patients can face exorbitant treatment costs, due to many insurers’ reimbursement policies that do not cover non-FDA-approved treatments, Wells says. In some cases, even if insurers cover off-label medications, some studies suggest that only 25% of patients with the condition can achieve satisfactory symptom control with standard medications.3 The difficulties and roadblocks experienced by patients, many of whom are too sleepy to fight for their right to proper treatments, is what inspired the Hypersomnia Foundation to establish the registry.

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How IH Differs from Narcolepsy Type 1 and 2

Although narcolepsy and idiopathic hypersomnia are both central disorders of hypersomnolence and share excessive daytime sleepiness as a key symptom, there are key differences in both the diagnostic processes and symptoms experienced by patients.

In a column called “Ask the Doctor” that appears on the Hypersomnia Foundation’s website, David Plante, MD, program director for the University of Wisconsin’s Sleep Medicine Fellowship program, discussed how providers use multiple sleep latency tests (MSLT) and polysomnography (PSG) to characterize hypersomnolence. As Plante advised, the distinction between idiopathic hypersomnia and narcolepsy lies in the number of sleep-onset REM periods (SOREMPs) that a patient experiences—patients with narcolepsy have two or more SOREMPs from PSG and MSLT results, whereas patients with idiopathic hypersomnia do not.4

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Unlike patients with narcolepsy, patients with idiopathic hypersomnia do not experience multiple SOREMPs or cataplexy. Idiopathic hypersomnia can occur either with or without a long sleep time, and, unlike patients with narcolepsy, patients with IH can sometimes repress daytime sleep bouts. And for patients with idiopathic hypersomnia, nocturnal sleep remains undisturbed, except for a delayed morning awakening.2

According to a two-year analysis of the hypersomnia registry from June 2016 through May 2018, 97.7% of participants experience excessive daytime sleepiness daily, 82.6% experience brain fog, 79% experience sleep inertia, and 71.8% experience poor memory. Other typical experiences included intentional and unintentional naps, daily long sleep, automatic behaviors, and the use of exceptionally loud, multiple alarms.1

Although narcolepsy and IH patients both experience exhaustion (due to their intense and persistent sleepiness), the registry analysis reveals that patients with type 2 narcolepsy (without cataplexy) took more intentional naps than those patients with IH. People with narcolepsy type 1 (with cataplexy) had more automatic behaviors and a higher frequency of deliberate and unintentional naps.1

The registry data also shows other notable differences, particularly regarding medication usage and perceived efficacy. Patients with IH were less likely to be treated with any medication for their excessive daytime sleepiness, and it was unknown which medications were most effective in treating IH. The most commonly reported medications were dextroamphetamine, followed by modafinil and methylphenidate.1

The retrospective analysis of data demonstrated significant value in having an IH patient-reported registry. There are still many questions that scientists have yet to answer. And that’s where you may be able to help. You can refer patients who have been diagnosed with IH or a related sleep disorder to the Hypersomnia Foundation’s International Patient Registry at CoRDS. Through this registry, patients can contribute to the collective understanding of IH and get connected to clinical trials and research studies. Learn more about the Hypersomnia Foundation International Patient Registry at CoRDS at

Yoona Ha is a freelance writer and healthcare public relations professional.


  1. Trotti LM, Ong JC, Plante DT, et al. Disease symptomatology and response to treatment in people with idiopathic hypersomnia: initial data from the Hypersomnia Foundation registry. Sleep Med. 2020 Sep 2;75:343-9.
  2. Billiard M, Dauvilliers Y. Idiopathic hypersomnia. Sleep Med Rev. 2001;5:349–58.
  3. Ali M, Auger RR, Slocumb NL, Morgenthaler TI. Idiopathic hypersomnia: clinical features and response to treatment. J Clin Sleep Med. 2009;5(6):562-8.
  4. Plante D. Ask the Doctor: Narcolepsy vs idiopathic hypersomnia. 2017 Jan 30.

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