EMBARGOED FOR RELEASE UNTIL 4 PM ET, July 18, 2018
Pregnancy History May Be Tied to Alzheimer鈥檚 Disease
Study Finds Links to Incomplete Pregnancies and Number of Children
MINNEAPOLIS -
A woman鈥檚 history of pregnancy may affect her risk of Alzheimer鈥檚 disease decades later, according to a study published in the July 18, 2018, online issue of , the medical journal of the 好色先生. The study found that women who give birth to five or more children may be more likely to develop Alzheimer鈥檚 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鈥檚 disease in the future than women who have never had an incomplete pregnancy. 鈥淓strogen levels double by the eighth week of pregnancy before climbing to up to 40 times the normal peak level,鈥 said study author Ki Woong Kim, MD, PhD, of Seoul National University in Seoul, South Korea. 鈥淚f 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鈥檚 disease based on the hormonal changes in the first trimester of pregnancy.鈥 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鈥檚 disease or its precursor, mild cognitive impairment. A total of 118 women developed Alzheimer鈥檚 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鈥檚 disease than women who gave birth to fewer children. Of the 716 women with five or more children, 59 developed Alzheimer鈥檚 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鈥檚 disease as women who had never had an incomplete pregnancy. Of the 2,375 women who had an incomplete pregnancy, 47 developed Alzheimer鈥檚 disease, compared to 71 of the 1,174 women who never had an incomplete pregnancy. On the tests of memory and thinking skills, women who had five or more children had lower scores than women who had fewer children. On a test where the maximum score is 30 points and scores of 24 or more indicate normal thinking skills and scores of 19 to 23 indicate mild cognitive problems, the women with five or more children had average scores of about 22 points, compared to almost 26 points for the women with fewer than five children. Women who had one or more incomplete pregnancies had higher test scores than women with no incomplete pregnancies, regardless of how many children they had. For example, among women with five or more children, those with no incomplete pregnancies had average scores of about 22, compared to scores of more than 23 points for those with one or more incomplete pregnancy. 鈥淚t鈥檚 possible that the modestly raised levels of estrogen in the first trimester of pregnancy are within the optimal range for protecting thinking skills,鈥 Kim said. A limitation of the study is that incomplete pregnancies may be been underestimated either because abortions were not reported or because women may not have realized that they had miscarriages. Another limitation is that the researchers did not collect information on the timing and cause of incomplete pregnancies. The study was funded by the Korean Ministry of Health and Welfare, Alzheimer鈥檚 Association, European Social Fund, Greek Ministry for Health and Social Solidarity, and National Health and Medical Research Council of Australia. Learn more about the brain at BrainandLife.org, the 好色先生鈥檚 free patient and caregiver magazine and website focused on the intersection of neurologic disease and brain health. Follow on , and .