Increased risk of dementia in patients with primary Sjogren's syndrome: a nationwide population-based cohort study.

Background/aims: This nationwide cohort study aimed to evaluate (1) whether primary Sjogren's syndrome (pSS) can contribute to the development of dementia and (2) whether the use of hydroxychloroquine (HCQ) can decrease the incidence of dementia in patients with pSS using the Health Insurance Review and Assessment database.

Methods: We established a cohort between 2008 and 2020 of 20,160 patients with pSS without a history of dementia. The control group comprised sex- and age-matched individuals with no history of autoimmune disease or dementia. Cox proportional hazard analyses were performed to identify the association between pSS and dementia development. We also assessed the hazard ratio (HR) of dementia in early users of HCQ (within 180 days of the diagnosis of pSS) compared to non-users, adjusted for age, sex, and comorbidities.

Results: The incidence of dementia was 0.68 (95% CI 0.64-0.72) cases per 100 person-years in pSS, and it was 0.58 (0.56-0.60) in the controls. The adjusted HR (aHR) of developing dementia was 1.16 (1.09-1.25) times greater in the pSS group than in the controls. The risk of dementia did not increase in HCQ users (aHR 1.07 [0.94-1.21]), but HCQ non-users had a 1.22 (1.12-1.33) higher risk of developing dementia than the matched controls. The use of HCQ lowered the risk of dementia in comparison with non-users in patients with pSS (aHR 0.82 [0.71-0.94]).

Conclusion: Our results suggest that pSS is associated with an increased risk of dementia. HCQ may prevent dementia in patients with pSS.