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

Abstract

OBJECTIVE Type 2 diabetes has been associated with high dementia risk. However, the links to different dementia subtypes is unclear. We examined to what extent type 2 diabetes is associated with dementia subtypes and whether such associations differed by glycemic control. RESEARCH DESIGN AND METHODS We used data from the Swedish National Diabetes Register and included 378,299 patients with type 2 diabetes and 1,886,022 control subjects matched for age, sex, and county randomly selected from the Swedish Total Population Register. The outcomes were incidence of Alzheimer disease, vascular dementia, and nonvascular dementia. The association of type 2 diabetes with dementia was stratified by baseline glycated hemoglobin (HbA1c) in patients with type 2 diabetes only. Cox regression was used to study the excess risk of outcomes. RESULTS Over the follow-up (median 6.8 years), dementia developed in 11,508 (3.0%) patients with type 2 diabetes and 52,244 (2.7%) control subjects. The strongest association was observed for vascular dementia, with patients with type 2 diabetes compared with control subjects having a hazard ratio [HR] of 1.34 (95% CI 1.28, 1.41). The association of type 2 diabetes with nonvascular dementia was more modest (HR 1.10 [95% CI 1.07, 1.13]). However, risk for Alzheimer disease was lower in patients with type 2 diabetes than in control subjects (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. CONCLUSIONS The association of type 2 diabetes with dementia differs by subtypes of dementia. The strongest detrimental association is observed for vascular dementia. Moreover, patients with type 2 diabetes with poor glycemic control have an increased risk of developing vascular and nonvascular dementia.