Upper Airway Resistance Syndrome (UARS) is a sleep-related breathing disorder that often goes unrecognized because it does not meet the criteria for full obstructive sleep apnea. This condition involves increased effort during breathing while sleeping, which ultimately disrupts the quality of rest. It is characterized by high resistance in the upper airway, forcing the body to work harder to pull air into the lungs. This increased effort causes subtle awakenings that fragment sleep, leading to various daytime consequences.
Defining Upper Airway Resistance Syndrome and Its Mechanism
Upper Airway Resistance Syndrome (UARS) occurs when the throat’s soft tissues, tongue, and jaw muscles relax during sleep, causing a narrowing, but not a complete collapse, of the upper airway. This partial obstruction significantly restricts airflow, requiring the body to increase the force of its inspiratory effort to overcome this resistance and maintain adequate oxygen intake. This heightened effort results in a change in intrathoracic pressure, which the brain senses as a struggle for air. To prevent the airway from collapsing completely, the brain initiates brief, momentary arousals known as Respiratory Effort-Related Arousals (RERAs). These RERAs are sequences of breaths lasting at least ten seconds that end in an arousal from sleep without a significant drop in blood oxygen levels, fragmenting the sleep architecture and preventing the deeper, restorative sleep stages.
Recognizing the Symptoms
The primary consequence of the fragmented sleep caused by RERAs is a pervasive sense of not being rested, which often manifests as excessive daytime sleepiness or chronic fatigue. Patients frequently report this fatigue is disproportionate to the number of hours they spend in bed. The constant, subtle interruptions prevent the brain from achieving the deep, restorative sleep necessary for feeling refreshed. Unrefreshing sleep and chronic insomnia are common, with many individuals struggling with difficulty both falling and staying asleep. Other symptoms can include headaches upon waking, mood disturbances like anxiety or depression, and snoring, though it is not always loud.
Distinguishing UARS from Obstructive Sleep Apnea
UARS falls on the spectrum of sleep-disordered breathing, between simple snoring and full Obstructive Sleep Apnea (OSA). The main difference lies in the severity of the obstruction and the resulting physiological impact. OSA involves full or near-full cessations of breathing, called apneas or hypopneas, which lead to significant drops in blood oxygen saturation. The severity of OSA is measured using the Apnea-Hypopnea Index (AHI), which counts the number of apneas and hypopneas per hour of sleep. In contrast, UARS is defined by a low or normal AHI, typically fewer than five events per hour, but with a high frequency of RERAs. Clinicians use the Respiratory Disturbance Index (RDI) to capture the severity of UARS, as the RDI includes the count of RERAs along with apneas and hypopneas. UARS patients are typically younger and may have a lower body mass index compared to those with OSA, and they often do not experience the significant oxygen desaturation that characterizes OSA.
Diagnosis and Treatment Approaches
Diagnosing Upper Airway Resistance Syndrome requires a specialized evaluation, as standard sleep studies focused only on AHI may miss the condition. The primary diagnostic tool is an in-laboratory polysomnography (PSG), or sleep study, which uses specialized sensors like nasal pressure transducers to detect subtle increases in respiratory effort and RERAs. The diagnosis is confirmed when the Respiratory Disturbance Index (RDI), which includes RERAs, is elevated, but the AHI remains low. Treatment aims to reduce upper airway resistance and stabilize breathing during sleep, often utilizing Continuous Positive Airway Pressure (CPAP) therapy to deliver pressurized air and keep the airway open. Alternative options include custom-fitted oral appliances, such as mandibular advancement devices, alongside lifestyle modifications like weight management, positional therapy, and avoiding alcohol before bed.