New research: Sleep regulation is disrupted in Idiopathic Hypersomnia

A new study published in SLEEP (2026) provides strong evidence that the body’s normal “sleep pressure” system doesn’t function properly in people living with Idiopathic Hypersomnia (IH).

This might sound technical, but it helps explain something many people with IH experience every day.

What is “sleep pressure”?

Sleep pressure is the brain’s built-in drive for sleep.

In a typical system, it:

• builds up while you’re awake

• reduces during sleep

• resets overnight so you wake up feeling relatively refreshed
  

It’s part of the body’s normal sleep–wake regulation.

In IH, this system doesn’t behave the way it should.

What this study found

This study shows that sleep pressure is dysregulated in IH, meaning both how it builds and how it reduces is disrupted.

Sleep pressure does not fully reduce after sleep Even after long periods of sleep, people with IH wake up with sleep pressure still there. This helps explain sleep inertia, “sleep drunkenness,” and feeling unrefreshed regardless of how long you sleep.

There are important differences between subtypes The study compared people with IH with long sleep time and without long sleep time.

In IH with long sleep time:

• sleep pressure does not reduce properly during sleep

• sleep pressure builds up faster during the day
  

In IH without long sleep time:

• sleep pressure does not reduce properly during sleep

• build-up during the day is not increased
  

In other words, both groups show dysregulation, but not in the same way.

“This doesn’t match my experience…”

A common reaction to this research has been:

“My sleep pressure is worst when I wake up and only slowly improves - if at all - during the day.”

This actually lines up very closely with what the study is showing.

If sleep pressure is not being reduced properly during sleep, you would expect to:

• wake up with high sleep pressure still present

• feel worst in the morning

• then gradually feel less bad as the day goes on
  

By the evening, some people feel more “awake”, not because everything is normal, but because they’ve moved out of that heavy sleep inertia phase. So, they feel 'normal' but still in the context of IH.

This is why IH can sometimes be mistaken for simply being a “night owl.” This research suggests it’s not preference — it’s biology.

Why sleeping more doesn’t fix it

One of the key points from this study is that the issue is not simply how long you sleep.

If sleep pressure is not being properly reduced during sleep:

• sleeping longer does not necessarily make you feel better

• but sleeping less would likely mean waking up with even more sleep pressure
  

This helps explain why long sleep is common in IH, but often unrefreshing.

Why this research matters

IH is often misunderstood as simply “being sleepy,” but this research suggests something deeper is going on — a disruption in how the brain regulates sleep need and recovery.

It also adds to growing evidence that IH is not one single condition. There are different patterns within IH, and recognising those differences matters for research, diagnosis, and future treatment approaches.

What this means for treatment

This study does not immediately change treatment guidelines.

That process takes time and a larger body of evidence.

However, it can still help inform how clinicians understand and manage IH, particularly in recognising different patterns of symptoms and thinking more individually about care.

It’s also important to note that treatment options depend on where you live. Even when guidelines exist, they don’t always translate into access if treatments are not approved or available in a particular country.

Where this leaves us

This research helps put a biological explanation behind something people with IH have been describing for a long time:

• waking up feeling awful

• taking hours to reach a more stable level of wakefulness

• and not feeling restored by sleep
  

The issue is not behaviour or motivation. It’s regulation.

And that’s where future research — and hopefully future treatments — need to focus.

Reference Adam T, Barateau L, Dauvilliers Y. Homeostatic dysregulation of slow wave activity during sleep in idiopathic hypersomnia. SLEEP. 2026.https://academic.oup.com/sleep/doi/10.1093/sleep/zsag060/8502076