Recently, the morbidity and mortality of cardiovascular disease has gradually been improved in people with diabetes (DM). This trend is largely due to the effective control of multiple risk factors associated with cardiovascular disease in DM patients. But paradoxically, the clinical importance of diseases such as neurodegenerative diseases of DM patients that were not very high priorities are rapidly increasing. In previous studies, DM has been found to play an important role in increasing the risk of dementia and cognitive dysfunction through various mechanisms. Although the mechanism is not known in detail, rapid changes in blood glucose including hypoglycemia are thought to directly affect dementia and cognitive dysfunction. However, research on related fields in Korea is still insufficient. Recently, we conducted a multicenter, prospective cohort study of Korean subjects. The causal relationship between hypoglycemia and dementia was analyzed in subjects 60 years of age or older. As the frequency of hypoglycemia increased, the risk of cognitive dysfunction including dementia was significantly increased. The results were consistent after adjusting for various confounders. In this lecture I will present our findings on behalf of our collaborators. And I will review key research findings in the relevant field, and discuss with the audience about the direction to improve the patient's clinical outcomes.