Age of Type 1 Diabetes Onset and Dementia Risk: A Swedish Nationwide, Register-Based Cohort Study

Individuals with Type 1 diabetes are at a higher risk of dementia compared to individuals without diabetes. Younger age at Type 1 diabetes onset has been linked to an increased risk of cardiovascular disease and higher mortality. This study aimed to determine whether younger age at Type 1 diabetes onset was also associated with all-cause dementia.

This nationwide prospective cohort study used data from individuals with Type 1 diabetes from the Swedish National Diabetes Register. All-cause dementia, including Alzheimer's disease, vascular dementia and non-Alzheimer's-non-vascular dementia, was prospectively ascertained as ICD-10 codes. Age at onset was stratified into < 10 years, 10-17 years and 18-30 years. The 18-30 years group was used as the reference group for all analyses. Cox regression modelling with age as the time-axis, from age at diabetes onset, was deployed to investigate dementia risk.

Of 43 440 included individuals (mean age 33.0 (SD 14.0) years; 44% female), Type 1 diabetes developed before age 10 in 11 776 individuals (27%), between age 10 and 17 in 15 846 (36%) and between 18 and 30 (reference group) in 15 818 (36%). During a median 29.3 [17.6-43.7] years follow-up, 530 (1.2%) developed all-cause dementia. Compared to the reference group, all-cause dementia risk was increased in individuals aged < 10 years at onset (HR 1.37 [95% CI 1.08-1.73]), but not in individuals aged 10-17 years at onset (HR 1.04 [95% CI 0.85-1.26]) (fully adjusted model).

Type 1 diabetes onset before age 10 is associated with an increased risk of all-cause dementia compared to onset between ages 18 and 30.