Women who have had their ovaries removed and carry a genetic mutation have an increased risk of developing Alzheimer’s disease.
- According to a new study, women who no longer have their ovaries before the age of 50 and who carry the APOE4 mutation have an increased risk of developing Alzheimer’s disease.
- Researchers have identified 3 factors that may reduce their risk of developing Alzheimer’s disease in these women.
- By 2050, Alzheimer’s disease is expected to affect 12.7 million people aged 65 and over.
For several years, scientists have noticed that women who have had their ovaries removed, a procedure called oophorectomy, have an increased risk of developing Alzheimer’s disease as they age. Researchers from the University of Toronto and the University of Alberta have conducted new research to better understand this phenomenon.
They discovered that it is women who underwent this operation before the age of 50 and carry a mutation in the apolipoprotein gene (the APOE4 allele) who have a high risk of developing the neurodegenerative disorder.
Alzheimer’s disease: oophorectomy and APOE4 mutation increase risks
For this study published in the journal Journal of Alzheimer’s Diseasethe team followed 34,603 women. She analyzed all of their medical records. Data shows that participants who had both ovaries surgically removed at around age 43 were four times more likely to develop Alzheimer’s disease compared to those who went through menopause naturally (at an average age of 54). .
The team believes they have found the origin of this increased risk of cognitive decline. “One of our most important findings was that loss of the natural (endogenous) hormone estradiol following surgical removal of both ovaries could interact with the APOE4 allele to further increase the risk of Alzheimer’s disease, placing women who have undergone early bilateral oophorectomy and carry APOE4 in a state of double danger“, explains Dr. Gillian Einstein, specifying that APOE4 is a known risk factor for Alzheimer’s disease in the general population, but poses a higher risk for women.
Alzheimer’s disease and oophorectomy: 3 resilience factors identified
In addition to shedding light on the risk factors for Alzheimer’s disease for women who have had their ovaries removed, the study helped identify their resilience factors. Researchers found that a high level of education was linked to a 9% reduced likelihood of developing Alzheimer’s disease in women who went through menopause naturally and via ovarian removal.
“Surprisingly, there was also a modest relationship between body mass index (BMI) and Alzheimer’s disease risk, but only for women who had early bilateral oophorectomy. Each additional unit of BMI was associated with a 7% lower risk of developing Alzheimer’s disease”write the authors in their press release. “Higher BMI may be associated with a decreased risk of Alzheimer’s disease in women who have had ovarian removal surgery because adipose tissue produces estrone (one of three endogenous estrogens ) which, in the absence of estradiol due to oophorectomy, may help maintain cognitive function in early middle age”specifies the first author, Dr Noelia Calvo.
Following hormonal therapy also reduces the risk of developing Alzheimer’s disease by half for women who no longer have their ovaries. On the other hand, this reduction in risks was not observed in naturally menopausal women taking hormone replacement therapy.
