A diabetes genetic risk score is associated with all cause dementia and clinically diagnosed vascular dementia in the Million Veteran Program

Objective: Diabetes and dementia are diseases of high healthcare burden worldwide, and studies have shown that diabetes is associated with increased relative risk of dementia. We set out to examine whether type 2 diabetes-associated genetic variants were associated with dementia and if they differed by race/ethnicity or clinical dementia diagnosis.

Research Design and Methods: We evaluated associations of two type 2 diabetes genetic risk scores (GRS and GRS-NonAPOE: a score without rs429358, a variant associated with Alzheimer’s disease [AD]) with three classifications of clinical dementia diagnoses in the Million Veteran Program (MVP): all-cause-dementia, vascular dementia (VaD), and AD. We conducted our analysis stratified by European (EUR), African (AFR), and Hispanic (HIS) race/ethnicities. Results: In EUR, we found associations of the GRS with all-cause-dementia (OR = 1.06, P = 1.60e-07), and clinically diagnosed VaD (OR = 1.12, P = 5.2e-05) but not clinically diagnosed AD (OR = 1.02, P = .43). The GRS was not associated with any dementia outcome in AFR or HIS. When testing with GRS-NonAPOE, we found that effect size estimates in EUR increased and P values decreased (for all-cause-dementia OR = 1.08, P = 2.6e-12; for VaD OR = 1.14, P = 7.2e-07and for AD OR = 1.06, P = .018). For AFR, the association of GRS-NonAPOE and clinically diagnosed VaD (OR = 1.15, P = .016) was statistically significant.  There were no significant findings for HIS. Conclusions: We found evidence suggesting shared genetic pathogenesis of diabetes with all-cause-dementia and clinically diagnosed VaD.