Diabetes mellitus is a risk factor for vascular dementia, but not for Alzheimer's disease: A population-based study of the oldest old

Background: The purpose of this study was to examine if Type 2 diabetes mellitus is a risk factor for dementia in very old age, specifically for Alzheimer's disease (AD) and vascular dementia (VaD). Methods: We evaluated the risk of dementia in relation to Type 2 diabetes using a population-based sample of 702 individuals aged 80 years and older (mean age 83 years). A total of 187 persons received a dementia diagnosis. Thirty-one individuals had a diabetes diagnosis prior to onset of the dementia. Results: Cox proportional hazard analyses, adjusted for age, gender, education, smoking habits, and circulatory diseases, indicated an elevated risk to develop VaD (relative risk = 2.54, 95% confidence interval 1.35-4.78) in individuals with diabetes mellitus. No association was found between diabetes and AD. Conclusion: Type 2 diabetes is selectively related to the different subtypes of dementia. There is no increased risk of AD but more than a twofold risk of VaD in persons with diabetes.