Assessment of Salivary Flow Patterns in Sjögren's Disease

OBJECTIVE: Salivary flow may follow a circadian rhythm regulated by clock genes and aquaporins. Because aquaporin 5 dysregulation may contribute to Sjögren's disease, we investigated whether daily unstimulated and stimulated salivary flow patterns differed between participants with Sjögren's disease and healthy controls. METHODS: Thirteen participants were recruited (80% power). Participants with Sjögren's disease met the 2016 American College of Rheumatology/European Alliance of Associations for Rheumatology classification criteria; healthy controls were not taking xerogenic medications. Saliva was collected at home (5:00 AM, 10:00 AM) and in the clinic (3:00 PM) for 5 min (unstimulated) and 2 min (stimulated). Differences were analysed using Friedman's test, the Mann-Whitney U test, and mixed-effects models (α = 0.05). RESULTS: We analysed 13 healthy controls (mean age 48.9 ± 10.7 years) and 13 participants with Sjögren's disease (mean age 65.3 ± 8.4 years). In the Sjögren's disease group, unstimulated flow did not vary over time (p = 0.463), but stimulated flow varied significantly across time points (p = 0.037). Neither measure varied significantly over time in controls (both p = 0.527). CONCLUSION: Neither group showed clear evidence of a circadian salivary flow pattern, and temporal patterns did not differ significantly between groups.