APOE4 refers to a specific allele of the apolipoprotein E (APOE) gene, which has been linked to an increased risk of developing Alzheimer's disease. Individuals who inherit one or two copies of the APOE4 allele are at a higher risk for developing the disease compared to those who do not have this genetic variant. Research in this area focuses on understanding the role of APOE4 in the pathogenesis of Alzheimer's disease, as well as potential therapeutic strategies to mitigate its effects on cognitive decline. Additionally, studies are being conducted to investigate the relationship between APOE4 and other health conditions, such as cardiovascular disease and cognitive impairment.