A study has found that consistently consuming ginseng (red ginseng) for five years or more can prevent cognitive decline caused by Alzheimer's disease. A research team led by Professors Kim Ji-wook, Seo Kook-hee, and Choi Young-min of the Department of Psychiatry at Hallym University Dongtan Sacred Heart Hospital, and Professor Kim Hyun-soo of the Department of Laboratory Medicine, examined the association between ginseng and cognitive function and the modulation of apolipoprotein E4 (APOE4), a gene known as the Alzheimer's gene, in 160 elderly individuals aged 65 to 90 without dementia. Ginseng intake was systematically assessed, including type, age of first consumption, duration, and frequency. A validated nutritional assessment method was also used to analyze dietary patterns based on protein, fruit, and vegetable types. Blood tests were also performed to determine the presence of apolipoprotein E4. The results showed that most of the ginseng consumed was steamed and dried red ginseng, and that ginseng consumption was found to have a protective effect on episodic memory, a cognitive decline associated with early Alzheimer's disease. Episodic memory, also known as "episodic memory," refers to the memory of when and where an event occurred. The protective effect was particularly pronounced in those who took ginseng for five years or more, or from middle age onward. However, the protective effect was diminished in those who carried the Alzheimer's disease gene, apolipoprotein E4.