Upper Airway Resistance Syndrome: More than 30 Years Later

Introduction: Upper airway resistance syndrome (UARS) is an underrecognized form of sleep-disordered breathing that predominantly affects young, non-obese individuals, particularly women.Unlike obstructive sleep apnea (OSA), UARS occurs in the absence of significant hypoxemia, yet it produces substantial impairment in quality of life and is frequently misdiagnosed as a psychiatric or functional disorder.Pathophysiology: Upper airway resistance syndrome is characterized by increased upper airway resistance leading to progressive respiratory effort and repetitive microarousals (RERAs).A hallmark feature is a low arousal threshold, whereby patients awaken in response to minimal increases in intrathoracic pressure before oxygen desaturation occurs.This sensory-motor dysfunction results in severe sleep fragmentation, neuroendocrine dysregulation, and autonomic imbalance, despite preserved oxygenation.Diagnosis: Clinical suspicion is essential, as conventional apnea-hypopnea indices are typically normal.Definitive diagnosis requires polysomnography (PSG) with detection of airflow limitation and RERAs.Esophageal manometry remains the gold standard for quantifying respiratory effort, although nasal pressure transducers provide a reliable, non-invasive alternative in routine practice.Treatment: Continuous positive airway pressure (CPAP) is the most effective therapy, significantly reducing microarousals and improving daytime symptoms, though adherence may be challenging.Mandibular advancement devices (MADs) and targeted upper airway surgery represent effective alternatives in selected patients.Management of comorbid insomnia and allergic airway disease is crucial.Discussion: Upper airway resistance syndrome is a distinct clinical entity rather than a mild variant of OSA.Early recognition and personalized, multidisciplinary treatment are essential to prevent progression to OSA and to reduce cardiometabolic risk, particularly resistant hypertension.Greater awareness of UARS may profoundly improve patient outcomes and redefine current paradigms in sleep medicine.