Toronto: Women who undergo bilateral oophorectomy (removal of both ovaries) before age 50, particularly those carrying the APOE4 allele—a variant of the apolipoprotein gene—face a significantly higher risk of developing Alzheimer’s disease later in life, according to a new study. The research, conducted by the University of Toronto in collaboration with the University of Alberta, was published in the Journal of Alzheimer’s Disease.
Analyzing data from 34,603 women in the UK Biobank, the study revealed that women who had their ovaries removed around the age of 43 were four times more likely to develop Alzheimer’s than those who experienced natural menopause at an average age of 54. This heightened risk was found to be associated with the loss of estradiol, a key hormone produced by the ovaries, which appears to interact with the APOE4 gene, amplifying susceptibility to Alzheimer’s.
“Loss of naturally occurring estradiol following ovary removal may place women with early oophorectomy and the APOE4 allele in a state of double jeopardy,” said Dr. Gillian Einstein, lead author of the study to IANS.
Alzheimer’s disproportionately affects women, who make up two-thirds of the projected 12.7 million Alzheimer’s cases expected in individuals aged 65 and older by 2050. The reasons behind this disparity remain unclear, but early-life factors such as ovary removal may play a role.
The study also highlighted the potential protective role of body mass index (BMI) in women with early ovarian removal. Researchers found that for these women, each additional unit of BMI was linked to a 7% lower risk of developing Alzheimer’s. Dr. Noelia Calvo of the University of Toronto explained that adipose tissue produces estrone, a type of estrogen, which may help compensate for the loss of estradiol, supporting cognitive function during early middle age.
The findings emphasize the importance of hormone-based therapies, particularly estrogen, for women who undergo early oophorectomy. Hormone therapy may help mitigate the increased risk of Alzheimer’s associated with estradiol loss and the APOE4 gene variant.