Associations between Retinal Markers of Microvascular Disease and Cognitive Impairment in Newly Diagnosed Type 2 Diabetes Mellitus: A Case Control Study

OBJECTIVE To investigate associations between retinal microvascular changes and cognitive impairment in newly diagnosed type 2 diabetes mellitus. DESIGN Case control study. SETTING A primary care cohort with newly diagnosed type 2 diabetes mellitus. METHODS For this analysis, we compared 69 cases with lowest decile scores (for the cohort) on the Modified Telephone Interview for Cognitive Status and 68 controls randomly selected from the remainder of the cohort. Retinal images were rated and the following measures compared between cases and controls: retinal vessel calibre, arterio-venous ratio, retinal fractal dimension, and simple and curvature retinal vessel tortuosity. RESULTS Total and venular (but not arteriolar) simple retinal vessel tortuosity levels were significantly higher in cases than controls (t = 2.45, p = 0.015; t = 2.53, p = 0.013 respectively). The associations persisted after adjustment for demographic factors, retinopathy, neuropathy, obesity and blood pressure. There were no other significant differences between cases and controls in retinal measures. CONCLUSIONS A novel association was found between higher venular tortuosity and cognitive impairment in newly diagnosed type 2 diabetes mellitus. This might be accounted for by factors such as hypoxia, thrombus formation, increased vasoendothelial growth factor release and inflammation affecting both the visible retinal and the unobserved cerebral microvasculature.