People who carry a newly identified variant of the APOE4 gene are more than 50 percent less likely to develop Alzheimer’s disease than non-carriers, a new study shows. Carriers of an APOE3 variant are more than 60 percent less likely to develop the disease.

Researchers analyzed the genetic makeup of more than 544,000 people. The participants included people who had been diagnosed with Alzheimer’s disease, those with a first-degree relative who had the disease, and those who were healthy.

The researchers found that two rare variants reduced the participants' risk of developing Alzheimer’s disease. Carriers of an APOE4 variant called R251G were 56 percent less likely to develop the disease, and carriers of an APOE3 variant called V236E were 63 percent less likely.

APOE is a protein involved in lipid transport. There are three known forms of the APOE gene that influence Alzheimer’s disease risk: APOE2, APOE3, and APOE4. APOE4 is the primary genetic risk factor for Alzheimer’s disease. Having one APOE4 allele typically increases a person’s Alzheimer’s disease risk as much as threefold; carrying two APOE4 alleles typically increases a person’s risk as much as 15-fold. However, this newly identified sub-type of APOE4 markedly alters that risk and adds complexity to discussions about the role of genetics in Alzheimer’s disease.

These findings suggest that some variants of the APOE gene may be protective against Alzheimer’s disease. Although genetics play key roles in Alzheimer’s disease risk, lifestyle does, too. Eating a healthy diet, exercising, meditating, and sauna use may forestall or even prevent the onset of the disease. Learn more about preventing Alzheimer’s disease in this episode featuring Dr. Dale Bredesen.

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