Upper Airway Resistance Syndrome (UARS) is a form of sleep-disordered breathing that exists on a spectrum between simple snoring and Obstructive Sleep Apnea (OSA). It is characterized by an increased effort required to breathe during sleep due to a narrowing of the upper airway. Unlike severe sleep apnea, UARS does not involve complete breathing pauses or severe drops in blood oxygen levels. However, this condition significantly impairs sleep quality by causing frequent, subtle awakenings that the sleeper may not consciously remember.
The Physiology of Upper Airway Resistance Syndrome
The physical mechanism of UARS involves the partial collapse or narrowing of the airway tissues, such as the soft palate and tongue base, when muscle tone naturally relaxes during sleep. This narrowing increases the resistance to airflow, similar to trying to breathe through a restricted opening. To overcome this elevated resistance, the chest and diaphragm muscles must work harder to draw air into the lungs, creating a greater negative pressure within the chest.
The body’s response to this increased respiratory effort is a brief awakening called a Respiratory Effort Related Arousal (RERA). A RERA is a short change in brain wave activity that pulls the person out of a deeper sleep stage to momentarily restore normal muscle tone and widen the airway. These micro-arousals occur repeatedly throughout the night, often without the person feeling fully awake. This constant cycle of effort and arousal severely compromises sleep quality, leading to highly fragmented and unrefreshing sleep.
Distinguishing UARS from Obstructive Sleep Apnea
UARS is formally differentiated from Obstructive Sleep Apnea based on specific measurement criteria established during a sleep study. The primary diagnostic metric for OSA is the Apnea-Hypopnea Index (AHI), which counts the number of apneas (complete breathing pauses) and hypopneas (significant partial airflow reductions with oxygen drops) per hour of sleep. A diagnosis of OSA is typically made when the AHI is five or greater events per hour.
Patients with UARS have an AHI score that is considered normal, usually fewer than five events per hour, and maintain minimum blood oxygen saturation levels above 92%. The disorder is defined by the frequent occurrence of Respiratory Effort Related Arousal (RERAs). The total number of apneas, hypopneas, and RERAs per hour is counted as the Respiratory Disturbance Index (RDI). A diagnosis of UARS is suggested when the AHI is low, but the RDI is elevated, indicating that sleep fragmentation is caused by breathing effort rather than severe oxygen desaturation.
Recognizable Signs and Daytime Consequences
The sleep fragmentation caused by repeated RERAs leads to a range of symptoms. The most common result is excessive daytime sleepiness, which persists despite sleeping for an adequate number of hours. Individuals frequently report feeling unrefreshed upon waking.
Cognitive effects are common, including difficulty concentrating, memory lapses, and reduced mental clarity, often described as “brain fog.” Morning headaches are another symptom, thought to be related to the disrupted sleep architecture. While snoring can be present, it is typically milder than in OSA. Because of the overlapping nature of the symptoms, UARS may be misdiagnosed as chronic fatigue, insomnia, or depression.
Diagnosis and Management Options
The definitive diagnosis of UARS requires a polysomnography, or full sleep study, conducted in a laboratory setting. This test must be sensitive enough to detect the subtle RERAs, requiring monitoring respiratory effort using specialized equipment, such as nasal pressure transducers. When the AHI is low but the RDI is elevated (typically five or more events per hour), UARS is the likely diagnosis.
Treatment aims to reduce upper airway resistance and eliminate RERAs, restoring restorative sleep. The most common treatment is Continuous Positive Airway Pressure (CPAP) therapy, which uses pressurized air to keep the airway open during sleep. Oral appliances, such as Mandibular Advancement Devices, provide an effective alternative by repositioning the lower jaw and tongue forward. Lifestyle modifications, including positional therapy and weight management, can also help alleviate symptoms.