Upper Airway Resistance Syndrome, Apnea's Quieter Cousin

What is upper airway resistance syndrome?

UARS happens when the airway narrows enough during sleep to make breathing effortful, without narrowing all the way to a full pause or a large oxygen drop. Instead of the countable apneas and hypopneas that define obstructive sleep apnea, someone with UARS has repeated brief arousals — the brain waking just enough to open the airway back up, often without the person remembering it happening at all. Those arousals fragment sleep the same way apnea events do, which is why the daytime effects can feel identical: fatigue, brain fog, and sleep that doesn't feel restorative no matter how many hours were spent in bed.

Respiratory effort-related arousals, or RERAs, are the specific events that define UARS — brief awakenings triggered by increasing effort to breathe against a narrowed airway, distinct from the breathing pauses (apneas) or partial reductions in airflow (hypopneas) that a standard sleep study counts toward an apnea diagnosis.

How is UARS actually different from obstructive sleep apnea?

Obstructive sleep apnea is graded using the apnea-hypopnea index, a count of breathing pauses and significant airflow reductions per hour of sleep, generated by the same kind of overnight polysomnography that serves as the diagnostic standard for sleep-disordered breathing 1Ref 1Kapur VK, Auckley DH, Chowdhuri S, Kuhlmann DC, Mehra R, Ramar K, Harrod CG (2017).Clinical Practice Guideline for Diagnostic Testing for Adult Obstructive Sleep Apnea: An American Academy of Sleep Medicine Clinical Practice Guideline.That polysomnography is the diagnostic standard for sleep-disordered breathing, and that a comprehensive sleep evaluation, rather than a default protocol, determines what a given study is set up to detect.. UARS can produce a completely normal or borderline apnea-hypopnea index, because the events driving it — brief increases in breathing effort — often don't meet the strict criteria counted toward that number, even though they're waking the brain just as disruptively.

a normal apnea-hypopnea index on a sleep study doesn't necessarily mean nothing is wrong with someone's breathing during sleep — it means the standard measure didn't catch what's happening. UARS and obstructive sleep apnea are often described as points on the same spectrum of airway narrowing rather than two unrelated conditions, with simple snoring at the milder end and severe apnea at the other; UARS sits somewhere in between, closer to snoring in its numbers but closer to apnea in how it disrupts sleep.

Why does UARS get missed or misdiagnosed so often?

Two things make UARS easy to overlook. First, the people who have it don't fit the profile clinicians are trained to associate with sleep apnea — they're often younger, thinner, and without the loud, obvious snoring that prompts an apnea workup in the first place, so the possibility of a breathing-related sleep problem may not come up at all. Second, when it is tested for, a standard sleep study reading focused on the apnea-hypopnea index can come back reassuringly normal, because that number isn't designed to capture repeated effort-related arousals.

The daytime symptoms — persistent fatigue, difficulty concentrating, unrefreshing sleep, sometimes anxiety or a racing mind at night — overlap heavily with chronic insomnia, and it's common for someone with undiagnosed UARS to be treated for insomnia for years without anyone examining whether an airway problem is driving the fragmented sleep underneath it.

How is UARS actually diagnosed?

Catching UARS generally requires more sensitive monitoring than a standard diagnostic study defaults to. A nasal pressure cannula, which can detect subtle flattening of the airflow signal that signals increasing airway resistance before a full apnea or hypopnea would be scored, is one commonly used tool; some sleep labs also use esophageal pressure monitoring, a more invasive but more precise way of directly measuring the effort someone is making to breathe against a narrowing airway. Neither is part of every routine sleep study by default, which is part of why UARS often requires a clinician who's specifically looking for it, rather than turning up incidentally on a standard test 1Ref 1Kapur VK, Auckley DH, Chowdhuri S, Kuhlmann DC, Mehra R, Ramar K, Harrod CG (2017).Clinical Practice Guideline for Diagnostic Testing for Adult Obstructive Sleep Apnea: An American Academy of Sleep Medicine Clinical Practice Guideline.That polysomnography is the diagnostic standard for sleep-disordered breathing, and that a comprehensive sleep evaluation, rather than a default protocol, determines what a given study is set up to detect..

Because the condition isn't captured by the apnea-hypopnea index the way obstructive sleep apnea is, there's no single widely agreed numeric cutoff that defines a UARS diagnosis the way there is for apnea severity — diagnosis leans more on the pattern of arousals and symptoms together than on one clean number.

What treatments are used for UARS?

Because UARS sits on the same airway-narrowing spectrum as obstructive sleep apnea, treatment tends to borrow directly from the OSA toolkit rather than following a separate, UARS-specific protocol. Positive airway pressure therapy, the guideline-recommended treatment for adults with obstructive sleep apnea 2Ref 2Patil SP, Ayappa IA, Caples SM, Kimoff RJ, Patel SR, Harrod CG (2019).Treatment of Adult Obstructive Sleep Apnea with Positive Airway Pressure: An American Academy of Sleep Medicine Clinical Practice Guideline.That positive airway pressure is the guideline-recommended treatment for adults with obstructive sleep apnea, the mechanism extended to UARS by clinical reasoning rather than dedicated UARS trials., is often tried for UARS as well, on the reasoning that the same mechanism — pressurized air keeping the airway open — should reduce the effort-related arousals even without a formal apnea diagnosis. A custom oral appliance, fitted by a dentist, is another option; the joint guideline covering oral appliance therapy specifically recommends it over no treatment at all for primary snoring, the milder end of the same spectrum UARS sits within 3Ref 3Ramar K, Dort LC, Katz SG, Lettieri CJ, Harrod CG, Thomas SM, Chervin RD (2015).Clinical Practice Guideline for the Treatment of Obstructive Sleep Apnea and Snoring with Oral Appliance Therapy: An Update for 2015.That oral appliance therapy is recommended over no treatment for primary snoring, the milder end of the airway-narrowing spectrum that UARS also sits within., which is part of why it's a reasonable option clinicians turn to for UARS as well.

Weight management, positional changes, and treating nasal congestion that narrows the airway further are also commonly part of the plan, similar to how milder cases of sleep-disordered breathing are approached generally.

Where the evidence runs thin, and why that's worth knowing

It's worth being direct about something: UARS does not have its own American Academy of Sleep Medicine clinical practice guideline the way obstructive sleep apnea does. The treatments described above are extended to UARS by clinical reasoning and by the fact that it sits on the same airway spectrum as conditions that are well studied, not because CPAP or oral appliances have been proven specifically for UARS in large trials the way they have for OSA. That's not a reason to dismiss the diagnosis — the arousals and daytime symptoms are real and measurable — but it does mean a clinician evaluating for UARS is working with a thinner evidence base and more clinical judgment than one evaluating for straightforward apnea, and it's a reasonable thing to ask about directly during an evaluation.