Background:  Diabetes is a risk factor for cerebrovascular disease and cognitive impairment. The anatomical basis for this is uncertain.

Methods: The Canadian Alliance for Healthy Hearts and Minds (CAHHM) collected brain and carotid magnetic resonance imaging (MRI) and two cognitive tests (DSST and MoCA) in a cross-sectional sample of men and women. Brain MRIs identified brain infarcts (BI), lacunar BI, high white matter hyperintensity (WMH), vascular brain injury (VBI - BI or high WMH) and small vessel VBI (lacunar BI or high WMH). Carotid MRIs estimated carotid wall volume, a measure of subclinical atherosclerosis. Cognitive scores were standardized to each site’s mean score, and cognitive impairment was identified by one or both test scores ≤ 1 standard deviation below the site’s mean score on that test.    

Results: The 7733 participants included 495 (6.4%) with diabetes, of whom 388 were taking diabetes drugs. After age and sex adjustment, diabetes was independently associated with BI (OR 1.53, 95%CI 1.05, 2.24), VBI (OR 1.64, 95%CI 1.26, 2.13), small vessel VBI (OR 1.67, 95%CI 1.28, 2.19) and cognitive impairment (OR 1.47, 95%CI 1.20, 1.80). The association between diabetes and small vessel VBI persisted after adjustment for cerebrovascular disease risk factors and non-lacunar infarcts (OR 1.52, 95%CI 1.15, 2.01), and the association with cognitive impairment persisted after adjustment for small vessel VBI (OR 1.27, 95%CI 1.03, 1.56).  

Conclusion: Small vessel disease characterizes much of the relationship between diabetes and VBI. However, additional factors are required to disentangle the relationship between diabetes and cognitive impairment.