Dementia and Alzheimer's disease risks in patients with autoimmune disorders

Aim: To investigate an association between autoimmune disorders (AID) and hospitalization for dementia and Alzheimer's disease, and to study whether the risk is associated with follow-up time and age. Methods: We followed up all individuals in Sweden without previous hospital admission for dementia and Alzheimer's disease, and with a primary or secondary diagnosis of an AID between 1 January 1964 and 31 December 2010, in the Swedish National Patient Register for dementia and Alzheimer's disease. The Swedish National Patient Register includes both inpatients and outpatients. We calculated standardized incidence ratios (SIR) for dementia and Alzheimer's disease, adjusted for individual variables, including age, sex and comorbidities. Results: A total of 788 103 individuals were admitted to hospital because of an autoimmune disorder without previous dementia and Alzheimer's disease. Among a total of 42 conditions of AID, 9998 dementia and Alzheimer's disease patients were identified with a SIR of 1.28 (95% CI 1.26–1.31). A total of 17 showed an increased risk, and of those the remaining, 14 conditions were still at risk, when dementia and Alzheimer's disease diagnosed in the year of AID diagnosed were excluded. The risks depended on the age at hospitalization for dementia and Alzheimer's disease. Conclusions: The present large study quantified the increased risks of dementia and Alzheimer's disease in patients with many types of AID. Geriatr Gerontol Int 2018; 18: 1350–1355