A preliminary double-blind placebo-controlled study in twenty patients with MCI or AD reported improvement in AD Assessment Scale-Cognitive subscale (ADAS-cog) scores in APOE ε4-negative patients receiving medium-chain triglycerides, which was not observed in APOE ε4-positive patients; higher ketone concentrations were associated with greater improvement in paragraph recall with MCT treatment compared to placebo among all participants [84]. This evidence concerns the gene APOE and Alzheimer disease.