Upper airway resistance syndrome: what it is and how it's diagnosed

Upper airway resistance syndrome (UARS) describes an airway that narrows during sleep enough to make breathing harder and wake the brain briefly, usually without the full breathing pauses or oxygen drops of classic obstructive sleep apnea. The American Academy of Sleep Medicine counts it as part of obstructive sleep apnea, and finding it generally takes an in-lab sleep study that records brain activity.

If you're exhausted and a basic test came back normal, it's worth raising with a sleep specialist.

What is upper airway resistance syndrome?

The name was first used in 1993 by the sleep researcher Guilleminault, who was investigating adults with heavy daytime sleepiness and no clear cause, according to a 2015 review in Sleep Science. The idea was that the airway can narrow enough to raise the effort of breathing without fully closing.

In a 2012 review in Respiration, Pépin and colleagues describe the hypothesis behind UARS: snoring plus repeated arousals linked to breathing effort, without oxygen desaturation, might still cause real symptoms, poorer quality of life and effects on the heart and blood vessels. That differs from classic sleep apnea, where the main driver of harm is thought to be repeated drops in oxygen.

On a sleep study, the pattern shows up as runs of breaths with flow limitation, a flattened airflow signal that suggests a narrowed airway, ending in a brief arousal. The AASM calls these events respiratory effort-related arousals, or RERAs.

What are the symptoms?

The 2015 review lists excessive daytime sleepiness, fatigue and fragmented sleep as the most frequent symptoms. It adds that people with UARS report several problems more often than people with sleep apnea, including:

• Trouble falling or staying asleep
• Headaches
• Low blood pressure on standing up (postural hypotension)
• Acid reflux
• Irritable bowel syndrome
• Anxiety

Pépin and colleagues note that daytime sleepiness, the main diagnostic feature, is often confused with tiredness in women, and that some symptoms closely resemble those of functional somatic syndromes. The 2015 review also says the proportion of women is significantly higher in UARS than in obstructive sleep apnea. Our article on sleep apnea in women covers why breathing problems in sleep are often missed in women. If your main complaint is feeling unrefreshed, see waking up tired for other causes to rule out.

Is UARS its own disorder or a form of sleep apnea?

UARS is usually classed as a form of obstructive sleep apnea, though the classification has been debated for three decades. Pépin's review says the International Classification of Sleep Disorders doesn't treat UARS as a distinct entity and reports UARS patients as a subgroup of obstructive sleep apnea. The 2015 review likewise says the AASM considers UARS part of obstructive sleep apnea.

The AASM's 2017 diagnostic guideline explains why. The third edition of the classification (ICSD-3) defines obstructive sleep apnea using a respiratory disturbance index (RDI), measured on an in-lab study. The threshold is 5 or more events an hour with typical symptoms, or 15 or more an hour with or without symptoms. Unlike the apnea-hypopnea index (AHI), the RDI includes RERAs. So in practice, someone with frequent RERAs and symptoms can meet the definition of obstructive sleep apnea on a full sleep study even if their apneas and hypopneas alone would look normal.

Researchers still disagree about the bigger picture. The 2015 review says some authors see UARS as a step on a continuum between simple snoring and sleep apnea, while others see it as a distinct syndrome with its own features. In a 2019 commentary, Guilleminault himself and a colleague argued that labels like OSA, UARS and the AHI are now largely historical, and that the real goal is to recognize sleep-disordered breathing earlier, including the kind that doesn't cause oxygen drops.

So you may hear UARS used by some clinicians and not by others. Either way, the underlying problem, a narrowed airway disturbing sleep, is something a sleep specialist can assess.

How is it diagnosed?

UARS is diagnosed with a sleep study that can see both breathing and sleep. The 2015 review says UARS is suspected in people with daytime sleepiness or tiredness who don't meet the criteria for sleep apnea but whose study shows signs of increased airway resistance, such as flow limitation, with arousals tied to breathing effort.

That has a practical consequence for testing at home. The AASM guideline explains that home sleep apnea tests don't typically record brain waves, eye movements or muscle tone, so they can't tell sleep from wake or detect arousals. Conventional home devices can't even detect hypopneas that are associated only with an arousal. RERAs depend on arousals, so a home test isn't designed to find them. A full in-lab study, called polysomnography, is the standard test. Our guide to the home sleep apnea test explains why a negative home test doesn't rule out a breathing problem.

Research studies have used extra tools as well. The 2015 review describes definitions based on esophageal pressure, measured with a thin catheter, or on flow limitation picked up by a nasal cannula. Different research groups have used different cutoffs, and the review notes there is no outcome data defining a cutoff for RERAs or the RDI.

If you've had a normal home test but still feel unrefreshed, snore or wake often, ask your doctor whether an in-lab study makes sense. Our article on snoring vs. sleep apnea lists the warning signs to mention.

How is UARS treated?

The evidence on how UARS is treated is limited. The 2015 review found 27 articles on UARS treatment, mostly case reports and case series, with no randomized controlled trials of CPAP in UARS.

CPAP is the best studied option. In those studies it improved daytime sleepiness, fatigue and the number of brief arousals. But the review says adherence was low, partly because some people didn't feel better, and in at least one follow-up study insurers refused to cover CPAP because UARS didn't meet their criteria.

Oral appliances seemed to help in case reports and small case series, but their effectiveness for UARS is not established. Surgery has been studied in small numbers too. A 2021 systematic review found only three eligible studies with 49 people, all at lower levels of evidence. Pooled with the authors' own case series, surgery was linked with better daytime sleepiness scores, though breathing indexes were unlikely to change. For the treatments used in sleep apnea more broadly, see sleep apnea treatments explained.

Do mouth tape or nasal strips help?

No, mouth tape and nasal strips are not treatments for UARS or sleep apnea, and they shouldn't be used to put off an assessment. If you have ongoing daytime sleepiness or fatigue, see a doctor or sleep specialist. Our safety page explains when mouth tape isn't appropriate.

This article is general information, not medical advice.

Read next

• Snoring vs. sleep apnea: how to tell the difference
• What is a home sleep apnea test?
• Waking up tired: common causes

* This content is for informational and educational purposes only and is not medical advice. It is not intended to diagnose, treat, cure or prevent any disease or health condition. Talk to a qualified healthcare provider about your health.