Silent upper airway resistance syndrome: prevalence in a mixed military population.

STUDY OBJECTIVES The upper airway resistance syndrome (UARS) is a recently described form of sleep-disordered breathing in which transient increases in upper airway resistance result in repetitive EEG arousals. UARS is not associated with apnea or diminished airflow, although snoring and excessive daytime somnolence (EDS) are common. This report describes a subset of patients with UARS diagnosed by polysomnography who do not manifest snoring, which we define as silent upper airway resistance syndrome (SUARS). DESIGN A retrospective review of all polysomnographies performed at our sleep disorders center during 2000. SETTING Sleep disorders center of a large, academic, military hospital. PATIENTS Our center serves military personnel, military retirees, and their dependent families. INTERVENTIONS Esophageal manometry during polysomnography was routinely performed on patients with hypersomnolence (Epworth sleepiness scale > 10) who demonstrated a total arousal index >or= 10/h and a respiratory disturbance index of < 5/h on prior polysomnography. UARS was definitely diagnosed in patients who demonstrated repetitive increased upper airway resistance (IUAR) associated with brief EEG arousals followed by normalization of esophageal pressure (Pes). IUAR was defined by a pattern of crescendo negative inspiratory Pes of <or= - 12 cm H(2)O. RESULTS During calendar year 2000, we performed 724 polysomnographies in 527 patients. Obstructive sleep apnea was diagnosed in 383 patients (72.6%), and 44 patients (8.4%) were found to have UARS. In four patients with UARS (0.8% of total and 9.1% of UARS), snoring was not reported by history or observed during polysomnography, and SUARS was ultimately diagnosed. CONCLUSIONS UARS may occur in the absence of clinically significant snoring and may be an occult cause of EDS. We report a prevalence of SUARS of 9% among UARS patients and nearly 1% of all patients studied for hypersomnolence by polysomnography.