Diabetes mellitus and the Risk of Dementia, Alzheimer’s Disease and Vascular Cognitive Impairment in the Canadian Study of Health and Aging

BACKGROUND: Conflicting results have been reported about the status of diabetes mellitus as a risk for Alzheimer's disease. We investigated the relationship between diabetes and incident dementia (including Alzheimer's disease and vascular cognitive impairment) in a 5-year longitudinal study. METHODS: Secondary analysis of the Canadian Study of Health and Aging, a representative cohort study of dementia in older Canadians. RESULTS: 5,574 subjects without cognitive impairment at baseline participated in 5-year follow-up. Diabetes mellitus at baseline was associated with incident vascular cognitive impairment (RR: 1.62; 95% CI: 1.12-2.33) and its subtypes, vascular dementia (RR: 2.03; 95% CI: 1.15-3.57), and vascular cognitive impairment not dementia (RR: 1.68; 95% CI: 1.01-2.78). Diabetes was not associated with mixed Alzheimer's/vascular dementia (RR: 0.87; 95% CI: 0.34-2.21), incident Alzheimer's disease (RR: 1.30; 95% CI: 0.83-2.03) or all dementias (RR: 1.26; 95% CI: 0.90-1.76). CONCLUSIONS: Despite increased recognition of the role of vascular factors in Alzheimer's disease, we did not find an association between diabetes and incident Alzheimer's disease, even though diabetes was associated with incident vascular cognitive impairment.