Population-Based Cohort Study on Dementia Risk in Patients with Type 1 Diabetes Mellitus

Background: The risk of dementia increases by 15–28% in patients with type 2 diabetes mellitus (DM). However, studies on dementia risk in type 1 DM have been neither comprehensive nor conclusive. Methods: We carried out a cohort study involving 1,077 patients registered to have type 1 DM from 1998 to 2009 and 32,310 matched non-DM controls who were selected from Taiwan National Health Insurance Claims. These participants were followed up from their first clinical appearance for type 1 DM treatment in 1998–2009 to the date of dementia diagnosis or the last day of 2011. The Cox proportional hazard model was employed to estimate the hazard ratio (HR) of dementia incidence. Results: The incidence rates of dementia reached 42.8 and 13.1 per 104 person-years for the type 1 DM and control groups respectively. The adjusted HR of dementia in patients with type 1 DM was estimated at 3.01 (95% CI 2.18–4.14) after adjustment for demographics, comorbidity, urbanization, monthly income, and annual frequency of ambulatory care visits. No significant difference in sex-specific HR was observed. Conclusions: The relative risk of developing dementia (118–314%) in patients with type 1 DM was much higher than the ­previously reported relative risk (15–28%) associated with type 2 DM.