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.