A two-phase cohort study of the sleep phenotype within primary Sjögren's syndrome and its clinical correlates

Objective. To characterise the sleep profile of patients with primary Sjögren's syndrome (pSS) and its relationship between hyper-somnolence and other clinical parameters. Methods. In phase one of the study, we utilised cross-sectional data on daytime hyper-somnolence from the United Kingdom Primary Sjögren's Syndrome Registry (UKPSSR) cohort (n=857, female=92.7%). Phase two relied on clinical data from a cohort of patients (n=30) with PSS, utilising symptom assessment questionnaires and sleep diaries. Results. Within the UKPSSR, daytime hyper-somnolence was prevalent (ESS, 8.2±5.1) amongst pSS patients with a positive correlation between daytime hyper-somnolence and fatigue (Spearman's r_s=0.42, p<0.0001). Amongst the clinical cohort, 100% of patients had problematic sleep. Participants with pSS awoke frequently (NWAK, 2.2±1.3), had difficulty in returning back to sleep (WASO, 59.9±50.2 min vs. normal of <30min) and a reduced sleep efficiency (SE, 65.7±18.5% vs. >85%). Fatigue (FIS, 82.4 ±33.5) and orthostatic symptoms (OGS, 6.7±3.7) remained high in these patients. Conclusion. Sleep disturbances are a problem in pSS, comprising difficulty in maintaining sleep, frequent awakenings throughout the night and difficulties in returning back to sleep. As such, the total time in bed without sleep is much greater and sleep efficiency greatly reduced. These patients in addition have a high symptomatic burden possibly contributing to and/or contributed by poor and disordered sleep.