UARS (Upper Airway Resistance Syndrome)
A condition where airway narrowing causes sleep fragmentation through increased respiratory effort and RERAs, without producing the apneas or hypopneas that register on standard AHI testing.
What Is UARS (Upper Airway Resistance Syndrome)?
Upper Airway Resistance Syndrome (UARS) is a condition where the upper airway is narrowed enough to increase respiratory effort and cause sleep-disrupting arousals, but not narrowed enough to produce the apneas or hypopneas that register on standard sleep testing. People with UARS typically have a normal or near-normal AHI but experience significant daytime symptoms including fatigue, unrefreshing sleep, morning headaches, and brain fog.
UARS was first described by Dr. Christian Guilleminault and represents the milder end of the sleep-disordered breathing spectrum. It is characterised by frequent RERAs (Respiratory Effort-Related Arousals) and elevated respiratory effort without the oxygen desaturations typically seen in obstructive sleep apnea.
UARS is notoriously underdiagnosed because standard sleep studies focus on AHI, which looks normal in UARS patients. Flow limitation analysis, using metrics like the Glasgow Index, FL Score, and NED, is the primary tool for identifying UARS on PAP therapy. AirwayLab was partly created to address this diagnostic gap by making flow limitation visible from data that patients already collect.
How AirwayLab Measures This
AirwayLab detects the flow limitation patterns characteristic of UARS using the Glasgow Index (breath shape scoring), FL Score (population-level flatness), NED (per-breath peak-to-mid flow ratio), and RERA detection (sequences of progressively flow-limited breaths). These metrics reveal the breathing disruption that AHI misses in UARS.
Try it with your dataFrequently Asked Questions
What is the difference between UARS and sleep apnea?
Both are forms of sleep-disordered breathing, but they differ in severity. In OSA, the airway collapses enough to cause apneas and hypopneas (scored by AHI). In UARS, the airway narrows but does not collapse fully, causing RERAs and increased respiratory effort without triggering AHI events. Symptoms can be equally debilitating in both conditions.
How is UARS diagnosed?
UARS is difficult to diagnose because standard sleep studies focus on AHI, which is typically normal in UARS. Diagnosis requires detecting RERAs (via esophageal manometry or flow limitation analysis) and correlating with symptoms. Flow limitation analysis from PAP SD card data, as provided by AirwayLab, can help identify the characteristic patterns.
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Medical Disclaimer
AirwayLab is not a medical device and is not FDA-cleared or CE-marked. It is provided for educational and informational purposes only. The analysis results should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult qualified healthcare providers regarding your sleep therapy and any changes to PAP settings.