Type 2 Diabetes, Glycemic Control, and Their Association With Dementia and Its Major Subtypes: Findings From the Swedish National Diabetes Register

Objective: Type 2 diabetes has been associated with high dementia risk. However, the links to different dementia sub-types is unclear. We examined to what extent type 2 diabetes is associated with dementia sub-types and whether such associations differed by glycemic control.

Research Design and Methods: We used data from national Swedish National Diabetes Register study and included 378,299 patients with type 2 diabetes and 1,886,022 controls matched for age, sex and county, randomly selected from the Swedish total population registry. The outcomes were incidence of Alzheimer’s dementia, vascular and non-vascular dementia. The association of type 2 diabetes with dementia was stratified by baseline glycated hemoglobin (HbA1c) in type 2 diabetes patients only. Cox regression was used to study the excess risk of outcomes.

Results: Over the follow-up (median 6.8 years), 11508 (3.0%) type 2 diabetes patients and 52,244 (2.7%) controls developed dementia. The strongest association was observed for vascular dementia: here, patients with type 2 diabetes had a HR of 1.34 [95% CI 1.28, 1.41] compared to controls without. The association of type 2 diabetes with non-vascular dementia was more modest (HR: 1.10 [95% CI 1.07, 1.13]). However, risk for Alzheimer’s disease was lower in type 2 diabetes patients compared to controls (HR: 0.94 [95% CI 0.90, 0.99]). When the analyses were stratified by circulating concentrations of HbA1c, a dose-response association was observed.

Conclusion: The association of type 2 diabetes with dementia differs by subtypes of the disease. The strongest detrimental association is observed for vascular dementia. Moreover, patients with type 2 diabetes with poor glycaemic control have an increased risk of developing vascular and non-vascular dementia.