Upper airway resistance syndrome (UARS) is a sleep-related breathing disorder where increased resistance to airflow in your upper airway repeatedly disrupts sleep, even though your oxygen levels stay mostly normal. Unlike obstructive sleep apnea (OSA), where the airway collapses enough to cause drops in blood oxygen, UARS involves subtler narrowing that forces your body to work harder to breathe. That extra effort triggers brief awakenings, called respiratory effort-related arousals (RERAs), that fragment your sleep without you ever realizing it. The result is chronic fatigue, unrefreshing sleep, and daytime impairment that can be surprisingly severe for a condition that often looks “normal” on standard testing.
How UARS Differs From Sleep Apnea
Sleep apnea severity is measured by counting how many times per hour your breathing fully stops (apneas) or significantly decreases (hypopneas). This count is your apnea-hypopnea index, or AHI. In UARS, the AHI is typically below 5, which would be classified as normal or “no sleep apnea” on most sleep studies. The key difference is what’s happening beneath that normal-looking number.
During a RERA, your airway narrows enough to restrict airflow without technically qualifying as an apnea or hypopnea. Your brain detects the increased breathing effort, fires off a brief arousal to restore normal airflow, and you fall back asleep within seconds. This cycle can repeat dozens of times per hour. A more specific definition of UARS includes an AHI below 5, oxygen saturation staying at or above 92%, and a RERA index of at least 5 events per hour. Your oxygen doesn’t drop the way it does in OSA, which is exactly why the condition slips past many screening tools.
What Causes It
UARS is rooted in the anatomy of your airway. The most common contributing features include a recessed jaw (retrognathia), narrow nasal passages, a high and narrow palate, and low muscle tone in the throat. Many people with UARS are not overweight, which sets them apart from the typical sleep apnea patient profile and often leads clinicians to overlook the possibility of a breathing disorder entirely.
These structural features tend to develop early. Children who breathe through their mouths during key growth years often develop a narrower palate, a longer face, and dental crowding. These craniofacial patterns carry into adulthood and predispose the airway to the kind of subtle collapse that defines UARS. The condition was first described by sleep researcher Christian Guilleminault in 1993, who identified a group of patients with excessive daytime sleepiness, abnormal respiratory effort during sleep, and no evidence of traditional sleep apnea.
Symptoms Beyond Sleepiness
The hallmark symptoms are unrefreshing sleep and excessive daytime fatigue. But research shows that UARS patients often report the highest degree of subjective impairment compared to both primary snorers and people with mild obstructive sleep apnea. In one study, UARS patients were the most impaired in daily functioning and perceived sleep quality, even though objective sleep measures didn’t always reflect the severity of their complaints. This mismatch between how terrible you feel and how “fine” your numbers look is one of the most frustrating aspects of the condition.
Beyond fatigue, UARS is closely linked to what researchers call functional somatic syndromes. Patients with UARS are significantly more likely to report symptoms associated with irritable bowel syndrome, and the condition overlaps with complaints like cold hands and feet, low blood pressure, headaches, and difficulty concentrating. These connections suggest that the repeated sleep disruptions from RERAs don’t just rob you of rest. They dysregulate the autonomic nervous system, the branch of your nervous system that controls blood pressure, digestion, heart rate, and temperature regulation. This is why some UARS patients feel systemically unwell in ways that seem unrelated to sleep.
Why It’s Hard to Diagnose
The biggest obstacle is that many sleep studies aren’t designed to catch UARS. Home sleep apnea tests, which are now the first-line screening tool for suspected sleep apnea, typically measure airflow, oxygen levels, and breathing effort in simplified ways. They’re good at detecting the oxygen drops and breathing pauses of OSA, but they often lack the sensitivity to identify RERAs. Since UARS doesn’t cause significant oxygen desaturation, these tests frequently come back normal.
An in-lab polysomnography (PSG) with a nasal pressure transducer is the most reliable way to detect UARS. This setup can identify the characteristic flattening of the inspiratory airflow pattern that signals increased airway resistance, along with the brief arousals that follow. A RERA is formally defined as a sequence of breaths lasting 10 seconds or more with increasing respiratory effort or flattening of the nasal pressure signal, not meeting criteria for an apnea or hypopnea, that ends with an arousal. Without specifically scoring RERAs and calculating the respiratory disturbance index (RDI), which adds RERAs to the AHI, UARS is invisible.
This diagnostic gap means many people with UARS spend years being told their sleep is fine, or they receive diagnoses of insomnia, chronic fatigue syndrome, depression, or anxiety before the underlying breathing issue is identified.
Treatment Options
Continuous positive airway pressure (CPAP) is the standard treatment for sleep-disordered breathing, but UARS patients often tolerate it poorly. Because their airway obstruction is relatively mild, even modest CPAP pressures can feel excessive. Exhaling against continuous pressure recruits abdominal muscles, can provoke anxiety, and sometimes destabilizes breathing patterns further. Side effects like dry mouth, nasal irritation, and the feeling of air swallowing (aerophagia) add up quickly for patients who may need only gentle support.
Bilevel positive airway pressure (BiPAP) is often a better fit. BiPAP delivers higher pressure when you inhale and lower pressure when you exhale, which reduces the discomfort of breathing against a constant stream of air. The higher inspiratory pressure directly combats the flow limitation in the upper airway, while the lower expiratory pressure makes breathing out feel more natural. Clinicians typically consider switching from CPAP to bilevel therapy when CPAP pressure approaches 15 cm of water, a level that most patients find uncomfortable to exhale against.
Structural and Orthodontic Approaches
Because UARS is fundamentally an anatomical problem, treatments that address airway structure can be particularly effective. Rapid maxillary expansion, a technique that widens a narrow palate, has shown strong results. In adults with sleep-disordered breathing, a technique called mini-implant-assisted rapid palatal expansion (MARPE) reduced the AHI by 65.3% in one multicenter trial, along with improvements in oxygen saturation and sleep quality. By widening the maxilla, nasal airflow improves and the vulnerability to airway collapse decreases. This approach is especially promising for the non-obese patients who make up much of the UARS population.
In children, palatal expansion has an even larger evidence base, with studies showing significant increases in upper airway, nasal, and throat dimensions alongside reductions in disordered breathing events and better sleep quality scores. Addressing the problem during growth years can prevent the craniofacial patterns that lead to UARS in adulthood.
Other non-PAP options include oral appliances that advance the lower jaw to open the airway, nasal surgery to address structural obstructions like a deviated septum, and myofunctional therapy, which involves exercises to strengthen tongue and throat muscles and improve resting tongue posture. Long-term success with CPAP alone has been variable in UARS patients, which is why many sleep specialists recommend exploring structural treatments rather than relying solely on nightly pressure therapy.