BACKGROUND The aim of this study was to determine trajectories of cognitive and cortical changes over time in middle-aged patients with type 1 diabetes and proliferative retinopathy. METHODS Twenty-five patients and 25 controls underwent neuropsychological assessment and neuroimaging twice in 3.56 ± 0.65 and 3.94 ± 0.91 years respectively (P = 0.098). Cognitive assessment included the domains of general cognitive ability, memory, information processing speed, executive functions, attention, motor and psychomotor speed. Symmetrized percent change in local cortical thickness, surface area, and volume was determined by FreeSurfer 6's vertex-wise GLM method. Analyses were performed uncorrected and corrected for baseline systolic blood pressure and depressive symptoms. RESULTS In patients versus controls, accelerated executive functions decline was accompanied by, but not related to, lower left frontal and temporal surface area, left parietal and right frontal thickness, and bilateral frontal and right posterior cingulate volume (all PFWE <0.05). In patients, lower executive performance was related to loss of right precuneus surface area (PFWE = 0.005). Higher HbA1c during follow-up was related to executive functions decline (r = -0.509, P = 0.016), and loss of left hemisphere surface area (rcorrected analysis = -0.555, P = 0.007). CONCLUSIONS After 3.5 years of follow-up middle-aged type 1 diabetes patients with proliferative retinopathy, mild focal changes in executive functions and cortical structure were found, which may indicate accelerated aging.