Past pregnancies affect later risk for Alzheimer’s disease

A woman’s risk of Alzheimer’s disease (AD) may be affected by her pregnancy history, even decades later, according to a study recently published in Neurology. In addition, women who have five or more children are more likely to develop AD, while those who have had an incomplete pregnancy through miscarriage or abortion are less likely to develop AD.

Researchers led by senior author Ki Woong Kim, MD, PhD, Seoul National University, Seoul, South Korea, used data from two, independent, population-based studies done in Korea and Greece. In all, 3,549 women (mean age: 71 years) were included. Women who were currently taking hormone replacement therapy or had a hysterectomy or oophorectomy were excluded.

Reproductive histories were self-reported. Subjects underwent a diagnostic exam, which included a Mini-Mental State Examination (MMSE) to assess the presence of dementia and mild cognitive impairment, an average of 46 years from the time their first child was born.

Researchers found that 118 women developed AD, and 896 had mild cognitive impairment. The 716 women who had five or more children were 70% more likely to develop AD than those who had fewer children, and these results held even after multivariate analysis. In the memory and thinking skills assessments, these women scored lower than those with fewer children (average scores: 22 vs 26 points, respectively). Among women without dementia, those with five or more completed pregnancies scored worse than those with one to four completed pregnancies (P < 0.001).

Conversely, women who had had an incomplete pregnancy (n=2,375) were half as likely to develop AD as those who had never had an incomplete pregnancy. Those who had one or more incomplete pregnancies had better MMSE scores compared with women who had never had an incomplete pregnancy (P=0.008).

“Estrogen levels double by the eighth week of pregnancy before climbing to up to 40 times the normal peak level,” said Dr. Kim. “It’s possible that the modestly raised levels of estrogen in the first trimester of pregnancy are within the optimal range for protecting thinking skills.

“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 AD based on the hormonal changes in the first trimester of pregnancy,” concluded Dr. Kim.

The study was funded by the Korean Ministry of Health and Welfare, Alzheimer’s Association, European Social Fund, Greek Ministry for Health and Social Solidarity, and National Health and Medical Research Council of Australia.