The goal of this clinical trial is to assess the degree of improvement in cognitive functions, including memory, attention, thinking, executive and language functions in diagnosed patients MCI and AD taking dimethyl fumarate 480 mg daily compared to patients taking placebo. Participant will be 55 to 90 years old, both genders. The main question it aims to answer is: Changing the degree of cognitive improvement based on the RBANS score among patients diagnosed with MCI and AD after completing dimethyl fumarate therapy test group compared to the placebo group.