Dr. Anne Marie Morse on Idiopathic Hypersomnia

Idiopathic hypersomnia is a sleep disorder that causes excessive daytime sleepiness, as well as difficulty being awakened from sleep. The idiopathic portion of its name means there is no clear cause. In this exclusive interview, neurologist and sleep specialist Dr. Anne Marie Morse provides a comprehensive and nuanced breakdown of idiopathic hypersomnia, from when it was first characterized and how it presents and affects daily life to what makes discerning its epidemiology so difficult. She also provides a call to action for both patients and health care providers to help them identify the signs of this negatively impactful sleep disorder.

Dr. Morse on Idiopathic Hypersomnia

When we’re talking about idiopathic hypersomnia, I always like to kind of reflect on some of the historical context around this condition. This is a condition that is relatively young, only first really characterized in the 1950s by Bedřich Roth, who initially described this term of sleep drunkenness. This is an extreme form of sleep inertia. What’s sleep inertia? If you don’t know what it is, we’ve all experienced it. If you’re in medicine, you did a residency. You know when you were on night float and you finally got out of it and you woke up that following day, but you didn’t, you just felt like you were hit by a truck and hit your alarm 32 times, and you don’t even remember it? That’s sleep inertia. It is that extreme desire to stay asleep and difficulty arousing from it.

Sleep drunkenness is an extreme form of that, where it’s not only all those symptoms but also combativeness. You can be discombobulated and confused.

So, you look at this very short history since 1956 and follow it forward, and what you find is since that period of time, this phenomenon of idiopathic hypersomnia has undergone either proposed or actual nomenclature changes 8 times. When you look at that, you can see where there can be a lot of confusion around what this condition actually is. And I commonly will reflect and quote one of my attendings when I was a resident who would say to me, “Anne Marie, do you know what idiopathic means?” And I would say, “Yeah, of course, it means that there’s a condition that we don’t fully understand the mechanism as to why the pathophysiology is contributing to this disorder, but there’s this disorder.” And she goes, “Oh, you sweet girl. No, it means, you, the doctor, are an idiot and the patient is pathetic.”

Unfortunately, we are still in this paradigm where I am unfortunately an idiot, and hopefully that will evolve to a better state in the near future. And our unfortunate patients are experiencing a pathetic existence because of our lack of knowledge and even lack of treatments being offered to them.

Now, in reality, idiopathic hypersomnia is a defined disorder, and it’s important for me to give all of this prelude to that because when you’re actually looking at what is the epidemiology of this condition currently, there are defined rationale around what this condition is. If I were to do actigraphy, so that’s where you’re wearing a wrist-worn device to see what your sleep-like schedule is, and you’re sleeping greater than 660 minutes on average in 24 hours, that would be consistent with idiopathic hypersomnia.

Alternatively, if I do a nighttime study, a polysomnography, with a following day multiple sleep latency test, MSLT, and you fall asleep on those naps and your average time of falling asleep is less than 8 minutes and you have less than 2 sleep-onset REM periods, meaning you go into REM sleep in 15 minutes or less, then you would be considered idiopathic hypersomnia. However, with that stated, most physicians still don’t necessarily know that.

So, when looking at what is the epidemiology? We actually don’t know. We don’t know because one, we went through too many nomenclature changes, and when we keep changing a nomenclature and a diagnostic criterion, we change who fits and who doesn’t. Number two, again, the doctor is an idiot. What we see in retrospective claims data is in fact that. Although there are defined criteria to say what idiopathic hypersomnia is, we find that more than 50% of people who carry this diagnosis never had sleep testing.

Therefore, we’re either utilizing really nifty things like the DSM-V text revision to potentially apply a diagnosis, or we just don’t know what the hell we’re doing and we’re applying a diagnosis that may or may not fit. Now, with that stated, because there are defined criteria to be able to say who may be this diagnosis, there have been other attempts to try and better characterize how many people might be affected with it.

Recently, there have been great efforts with people like David Plante and Emmanuel Mignot who have looked at the Wisconsin Sleep Cohort, which is a very well-characterized patient population, and said, based on all this information, including really good sleep data, what percentage of this population would represent idiopathic hypersomnia? What did they find? They found it was about 1.5%. Think about that. Idiopathic hypersomnia is technically considered a rare disease where amongst our field, we argue as to whether or not it’s more or less prevalent than narcolepsy. Where narcolepsy, again, it’s about 1 in 2000 individuals, and this is saying it’s 1.5%.

If we were to apply that to a general population, I would like to give you an analogy that epilepsy affects 1% of the general population. Epilepsy is something we all know, we recognize, we treat. We aggressively treat it because we recognize that there are major risks to your health and wellness by not doing so. Idiopathic hypersomnia is the same thing. This is more than just being too tired. This is a condition where there is significant sleepiness. Many times, there may be an increased sleep need. It’s not uncommon after sleeping greater than age-appropriate duration, but they also are dreading sleep because it never feels restorative.

They dread taking a nap because they can’t take a short nap, and even when they wake from it, they feel worse than what they did. There’s significant brain fog, a term that has been popularized by long Covid where we don’t even actually have a technical definition for it, but we recognize that this is a discrete cognitive disability that is separate from mental fatigue or a specific cognitive deficit and really almost as described as feeling like my head isn’t attached to my body. I have difficulty processing and thinking and word finding, and you name the accumulation of deficits.

With that stated, this condition affects 24 hours of a day, and as we’re starting to look forward and better understand what else it is affecting, we’re seeing similar patterns to what we found with narcolepsy, where it not only affects your sleep wake, it also is affecting all of health, mental health, physical health, increased risk of mental health disorders, increased risk of cardiovascular disease, diabetes, obesity, pain syndromes, and so, therefore, is definitely a disorder that we all need to be on the lookout for.

When we think about epidemiologically, if we are saying who’s coming into our sleep clinics, this has been analyzed. There was a beautiful study done in around 1983, and it repeated in 2000, looking at over a dozen sleep centers across the United States. They found the top 3 diagnoses were obstructive sleep apnea (OSA), narcolepsy, and restless leg. However, when you looked at the distribution, 20%, 20, two-zero, represented narcolepsy and idiopathic hypersomnia. Twenty percent of the patients seen in these clinics.

Does that surprise me? Absolutely not. Why? Because more than 20% of the US population is sleepy. So, the call to action that you have today is sleepy is never normal. It’s common but never normal. Don’t mistake those 2 things. Common and normal are not the same. The second call to action is when you see sleepiness, think of your hypersomnolence disorders, including idiopathic hypersomnia. These are conditions that are treatable conditions and in fact can masquerade around as other sleep disorders, because both narcolepsy and IH have high comorbidity with OSA.

If you still have that sleepy individual in front of you who was already diagnosed with OSA, think beyond. If they have other conditions and they’re still sleepy, meaning they’re falling asleep, having difficulty staying awake, not fatigued or tired, sleeping, make sure you’re looking for things like idiopathic hypersomnia and narcolepsy. These are treatable conditions, and you can transform someone’s life by actually being able to diagnose them appropriately and get them on the right treatment track.