Dementia Risk in People With Type 1 Diabetes and Associated Risk Factors: A Nationwide, Register-Based Cohort Study

OBJECTIVE: Life expectancy of individuals with type 1 diabetes has increased, extending exposure to age-related conditions including dementia. Although earlier studies have linked type 1 diabetes with higher dementia risk, the relationships with dementia subtypes and associated risk factors are incompletely understood. RESEARCH DESIGN AND METHODS: In this cohort study, 43,440 individuals with type 1 diabetes from the Swedish National Diabetes Register and 217,109 age-, sex-, and county-matched control individuals from the Swedish Total Population Register were included. Cox regression was used to study the relation between type 1 diabetes and risk of all-cause dementia and dementia subtypes (Alzheimer disease, vascular dementia, and non-Alzheimer-nonvascular dementia). We also examined the relationship between various risk factors and risk of all-cause dementia in type 1 diabetes. RESULTS: After a median follow-up time of 14.3 (7.9-20.0) years, dementia was recorded in 530 (1.2%) individuals with type 1 diabetes and 1,867 (0.9%) age-, sex-, and county-matched control individuals (mean baseline age 33.0 [14.0] years). Compared with control individuals, individuals with type 1 diabetes had a higher risk of all-cause dementia (hazard ratio [HR] 2.02 [95% CI 1.83-2.23], Alzheimer disease (HR 1.38 [95% CI 1.13-1.69]), vascular dementia (HR 3.73 [95% CI 3.07-4.52]) and non-Alzheimer-nonvascular dementia (HR 1.87 [95% CI 1.63-2.15]). Risk factors related to dementia risk in type 1 diabetes beyond age were lower education level, being single, higher systolic blood pressure, higher HbA1c, history of stroke or transient ischemic attack, history of cardiovascular disease, and longer diabetes duration. CONCLUSIONS: The risk of all-cause dementia and dementia subtypes is higher in individuals with type 1 diabetes compared with matched control individuals.