The upper airway resistance syndrome.

Obstructive sleep apnea syndrome has been recognized as a major public health problem. Both its cardiovascular and metabolic comorbidities and symptoms motivate for an accurate diagnosis and appropriate treatment. The main stimulus associated with obstructive sleep apnea (OSA) and explaining deleterious consequences is intermittent hypoxia. The upper airway resistance syndrome (UARS) has been described based on the hypothesis that snoring and repetitive occurrence of respiratory effort-related arousals (RERAs) but not oxygen desaturation might produce a significant disease with symptoms, altered quality of life and cardiovascular morbidity. Diurnal sleepiness remains the main diagnostic criteria, which is often confounded with tiredness in women. UARS patients may also report insomnia and symptoms that closely resemble those of the functional somatic syndromes. Currently, the International Classification of Sleep Disorders does not individualize UARS as a specific entity and reports UARS patients as a subgroup of OSA. However, RERAs are described as unambiguous abnormal respiratory events occurring during sleep and requiring a specific scoring. In this review, the authors attempt to describe the specific characteristics of UARS that are relevant for both clinicians and researchers.