Upper airway surface tension but not upper airway collapsibility is elevated in primary Sjögren's syndrome

Abstract

Study objectives: Primary Sjögren's syndrome is an autoimmune disease typified by xerostomia (dry mouth) that, in turn, could lead to increased saliva surface tension (γ) and increased upper airway collapsibility. Fatigue, of unknown etiology, is also frequently reported by patients with primary Sjögren's syndrome. Recent preliminary data indicate a high prevalence of obstructive sleep apnea in healthy-weight women with primary Sjögren's syndrome. Concurrent research highlights a significant role of γ in the maintenance of upper airway patency. The aim of this study was to compare oral mucosal wetness, saliva γ, and upper airway collapsibility during wake and sleep between women with primary Sjögren's syndrome and matched control subjects. Setting: Participants slept in a sound-insulated room with physiologic measurements controlled from an adjacent room. Participants: Eleven women with primary Sjögren's syndrome and 8 age- and body mass index-matched control women. Interventions: Upper airway collapsibility index (minimum choanal-epiglottic pressure expressed as a percentage of delivered choanal pressure) was determined from brief negative-pressure pulses delivered to the upper airway during early inspiration in wakefulness and sleep. Measurements and Results: Patients with primary Sjögren's syndrome had significantly higher saliva γ ("pull-off" force method) compared with control subjects (67.2 ± 1.1 mN/m versus 63.2 ± 1.7 mN/m, P < 0.05). Upper airway collapsibility index significantly increased from wake to sleep (Stage 2 and slow wave sleep) but was not different between groups during wake (primary Sjögren's syndrome versus controls; 36.3% ± 8.0% vs 46.0 ± 13.8%), stage 2 sleep (53.1% ± 11.9% vs 63.4% ± 7.2%), or slow-wave sleep (60.8% ± 12.2% vs 60.5% ± 9.3%). Conclusions: Despite having a significantly "stickier" upper airway, patients with primary Sjögren's syndrome do not appear to have abnormal upper airway collapsibility, at least as determined from upper airway collapsibility index.