Diabetes and coronary artery disease as risk factors for dementia

Diabetes is associated with an increased risk of dementia, but it is still debated to which degree this risk depends on the presence of atherosclerotic cardiovascular disease (CVD). In this study, we hypothesize that patients with diabetes and coexisting coronary artery disease (CAD), as a marker of systemic atherosclerotic CVD, have a substantially higher risk of developing dementia.

Patients ≥65 years, who underwent coronary angiography, were stratified by diabetes and CAD. Outcomes were all-cause dementia, Alzheimer's dementia, and vascular dementia. We estimated adjusted hazard ratios (aHRs) using patients with neither diabetes nor CAD as a reference. A total of 103 859 patients were included. Of these, 23 189 (22%) had neither diabetes nor CAD, 3876 (4%) had diabetes, 61 020 (59%) had CAD, and 15 774 (15%) had diabetes and CAD. During a median follow-up of 6.3 years, 5592 (5.5%) patients were diagnosed with all-cause dementia. Patients with diabetes and CAD had the highest HR of all-cause dementia [aHR 1.37, 95% confidence interval (CI) 1.24-1.51], including Alzheimer's dementia (aHR 1.41, 95% CI 1.23-1.62) and vascular dementia (aHR 2.03, 95% CI 1.69-2.45). Patients with diabetes alone (aHR 1.14, 95% CI 0.97-1.33) or CAD alone (aHR 1.11, 95% CI 1.03-1.20) had a modestly increased rate of all-cause dementia.

The combination of diabetes and CAD is associated with an increased rate of dementia, in particular vascular dementia, suggesting that the diabetes-related risk of dementia is partly mediated through concomitant atherosclerotic CVD. This underscores the importance of atherosclerotic CVD prevention in diabetic patients to reduce cognitive decline.