A woman’s history of pregnancy may affect her risk of Alzheimer’s disease decades later, according to a study published in the July 18, 2018, online issue of Neurology, the medical journal of the American Academy of Neurology.
The study found that women who give birth to five or more children may be more likely to develop Alzheimer’s disease than women who have fewer births.
The study also showed that women who have had an incomplete pregnancy, whether through miscarriage or abortion, are less likely to develop Alzheimer’s disease in the future than women who have never had an incomplete pregnancy.
“Estrogen levels double by the eighth week of pregnancy before climbing to up to 40 times the normal peak level,” said study author Ki Woong Kim, MD, Ph.D., of Seoul National University in Seoul, South Korea.
“If these results are confirmed in other populations, it is possible that these findings could lead to the development of hormone-based preventive strategies for Alzheimer’s disease based on the hormonal changes in the first trimester of pregnancy.”
For the study, researchers combined the data from two, independent population-based studies from Korea and Greece, with a total of 3,549 women.
Women who were currently taking hormone replacement therapy and those who had a hysterectomy or surgery to remove the ovaries were not included in the study.
The women, who were an average age of about 71 at the start of the study, provided information on their reproductive history. They took the diagnostic examination after an average of 46 years from their first childbirth.
During that time, the participants took tests of their memory and thinking skills to see whether they had developed Alzheimer’s disease or its precursor, mild cognitive impairment. A total of 118 women developed Alzheimer’s disease and 896 women developed mild cognitive impairment.
Women who had given birth to five or more children were 70 percent more likely to develop Alzheimer’s disease than women who gave birth to fewer children.
Of the 716 women with five or more children, 59 developed Alzheimer’s disease, compared to 53 of the 2,751 women with fewer children. The results stayed the same after researchers adjusted for other factors, such as other medical conditions, use of hormone replacement therapy and breastfeeding.
Women who had experienced an incomplete pregnancy were about half as likely to develop Alzheimer’s disease as women who had never had an incomplete pregnancy.
Of the 2,375 women who had an incomplete pregnancy, 47 developed Alzheimer’s disease, compared to 71 of the 1,174 women who never had an incomplete pregnancy.