This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.The upper airway resistance syndrome (UARS) was first described in 19931 as a form of sleep disordered breathing distinct from sleep apnea/hypopnea syndrome. Based upon the early descriptions of UARS, it differed from sleep apnea chiefly in the severity of inspiratory flow limitation during sleep observed in the two syndromes. UARS patients were observed to have higher inspiratory airflows during sleep with lesser oxy-hemoglobin desaturation than sleep apnea patients, but had recurrent arousals and daytime hyper-somnolence (similar to sleep apnea patients). Subsequent research demonstrated that UARS patients differ from sleep apnea patients not only in their inspiratory airflow dynamics during sleep, but also in other symptoms and signs. Specifically, UARS patients have a high prevalence of sleep onset insomnia, irritable bowel syndrome, headaches (migraine and tension-type) and alpha wave intrusion into NREM sleep2. Despite the evidence supporting the existence of a sleep disordered breathing syndrome discrete from sleep apnea, some researchers question whether UARS should be considered a medical syndrome.3 Rather, they view UARS as mild hypopnea and not as a discrete pathophysiology. Their doubt is based upon a lack of evidence that inspiratory flow limitation during sleep is associated with the symptoms of UARS patients. They argue that inspiratory flow limitation during sleep can be observed in individuals who lack the symptoms of UARS patients. Further, they argue that the improvement in the hyper-somnolence of UARS patients after nasal continuous positive airway pressure (CPAP) treatment has never been tested against a placebo nasal CPAP treatment. Thus, the existence of UARS as a distinctive diagnosis necessitating treatment remains controversial.
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