Upper Airway Resistance Syndrome | Are You Chronically Tired Despite a Full Night's Sleep?

Upper Airway Resistance Syndrome (UARS) is a clinical condition that falls within the spectrum of sleep-disordered breathing, positioned between simple snoring and obstructive sleep apnea (OSA). It is characterized by a subtle narrowing of the upper airway during sleep. This narrowing does not cause a full cessation of breathing (apnea) or a significant decrease in airflow (hypopnea), which are the hallmarks of OSA. Instead, it forces the individual to exert significantly more effort to breathe. This increased respiratory effort leads to brief, frequent awakenings from sleep known as "respiratory effort-related arousals" (RERAs). The brain must arouse itself from deeper sleep stages to a lighter stage to restore normal muscle tone to the airway and overcome the resistance. A key feature of UARS is that these disturbances occur without notable drops in blood oxygen saturation, a common metric used to diagnose OSA. Consequently, individuals with UARS experience a highly fragmented sleep architecture. While they may technically sleep for seven or eight hours, the constant arousals prevent them from obtaining the restorative, deep stages of sleep necessary for proper physical and cognitive function. This leads to profound daytime sleepiness and fatigue, even when standard sleep apnea tests appear normal or show only mild abnormalities.

The primary distinction between UARS and Obstructive Sleep Apnea (OSA) lies in the specific type of respiratory events that define each condition. OSA is diagnosed based on the Apnea-Hypopnea Index (AHI), which quantifies the number of apneas and hypopneas per hour of sleep, typically accompanied by significant oxygen desaturation. In contrast, UARS is defined by the presence of RERAs. RERAs are periods of increasing respiratory effort that culminate in an arousal from sleep, but they do not meet the criteria for an apnea or hypopnea. Because UARS does not cause substantial dips in oxygen levels, it is often missed by standard home sleep tests and even some laboratory-based sleep studies (polysomnography) that are not scored with a specific focus on detecting subtle respiratory effort. The clinical presentation also differs. While there is overlap, the classic OSA patient is often an overweight, middle-aged male. The typical UARS patient is frequently a younger woman of normal weight, sometimes with specific craniofacial traits like a narrow palate or a recessed jaw that predispose them to airway narrowing.

The cardinal symptom of UARS is severe, persistent daytime fatigue and sleepiness that is disproportionate to the findings on a standard sleep study. Patients often report feeling "unrefreshed" upon waking, regardless of how long they slept. Other common cognitive symptoms include brain fog, difficulty with concentration and memory, and irritability. Morning headaches are also a frequent complaint, likely resulting from the sustained effort of breathing against a narrow airway all night. Paradoxically, some individuals with UARS may present with insomnia, particularly difficulty maintaining sleep, due to the frequent, subconscious arousals that interrupt sleep continuity. These symptoms significantly impact quality of life, academic performance, and professional productivity.

UARS can affect anyone, but it demonstrates a notable prevalence in certain demographics that differ from the typical OSA population. It is more commonly diagnosed in women and individuals with a normal or low body mass index (BMI). Anatomical factors play a crucial role in the predisposition to UARS. These include craniofacial features that result in a smaller or more collapsible airway, such as a high-arched hard palate, a small or recessed jaw (retrognathia), a large tongue in relation to the oral cavity, or dental crowding. These structural traits mean that even a small degree of muscle relaxation during sleep can lead to significant airway resistance. Hormonal factors may also play a role, contributing to its prevalence in women.

The definitive diagnosis of Upper Airway Resistance Syndrome requires a comprehensive, in-laboratory polysomnogram (PSG) that is meticulously scored for RERAs. The gold standard for detecting increased respiratory effort is esophageal manometry (Pes), which involves placing a pressure-sensing catheter into the esophagus. However, this method is invasive and not widely used in clinical practice. Instead, technicians rely on sensitive nasal pressure transducers and analysis of the airflow signal shape (flow limitation) to identify periods of escalating breathing effort that lead to arousals. Treatment for UARS is primarily aimed at preventing the collapse and narrowing of the airway during sleep. Continuous Positive Airway Pressure (CPAP) therapy, which uses pressurized air to act as a pneumatic splint for the airway, is highly effective. Often, individuals with UARS respond well to lower pressure settings compared to those with OSA. Another primary treatment is oral appliance therapy, where a custom-fitted dental device is worn during sleep to advance the lower jaw, thereby opening the airway. For some, surgical procedures to address specific anatomical obstructions, such as nasal septoplasty or tonsillectomy, may be beneficial.