Background: Diabetes has been shown as a risk factor for cognitive impairments. However, it is still not clear about the time course of developing abnormal cognition in those with diabetes especially if the morbidity accelerates the cognitive deterioration process. Objective: To study how diabetes is related to the abnormal cognition development. Methods: A retrospective analysis was performed using data collected by the National Alzheimer's Coordinating Center. Incidence, prevalence, and age at onset (AAO) of either mild cognitive impairment (MCI) or dementia were compared between participants with and without diabetes. Results: During a follow-up period of more than 10 years, the diabetic group had a higher incidence and prevalence of MCI or dementia than the non-diabetic group. However, the AAO of either MCI or dementia was independent of the diagnosis of diabetes. Conclusion: Although diabetic patients have a higher incidence and prevalence of abnormal cognition than those without diabetes, diabetes does not accelerate the cognitive deterioration process.