The issues related to gender and Alzheimer’s disease were a primary topic at this year’s Alzheimer’s Association International Conference held in Chicago in July. Research discussing a woman’s reproductive history that showed an association to the risk of dementia was presented.

Another study along the same lines discussed a relationship between the total months of pregnancy and having Alzheimer’s disease.

Representatives from the organization comment about the findings, "More research is needed in this area, because having a better understanding of sex-specific risk factors across the lifespan may help us discover — and eventually apply — specific prevention strategies for different populations of people with Alzheimer’s and other dementias," said Alzheimer's Association Chief Science Officer Dr. Maria Carrillo.

"More women than men have Alzheimer’s disease or other dementias; almost two-thirds of Americans with Alzheimer’s are women," said Carrillo. "According to Alzheimer’s Association 2018 Alzheimer's Disease Facts and Figures, of the 5.5 million people age 65 or older with Alzheimer’s in the United States, 3.4 million are women and 2.0 million are men."

Historically, the differences in the rate of Alzheimer’s disease between genders had been accounted for because women lived longer than men and age has always been the greatest risk factor. Now other factors such as biological influence of hormones and genetic variation are being considered as factors, as well as different life experiences such as education, occupation and incidence of cardiovascular disease.

The work related to reproductive history was done by a group which included Paola Gilsanz, ScD, staff scientist at Kaiser Permanente Northern California Division of Research in Oakland, California, and Dr. Rachel Whitmer, professor at UC Davis.

They used a large scale epidemiological approach reviewing multiple locations in the U.S. for data related to reproductive history and dementia risk. They found that there was a correlation between risk of dementia and the number of children, the number of miscarriages, the age at the time of first menstrual period, the age of onset of natural menopause and the total number of years between first menstrual cycle and menopause.

They looked at 14,595 women between the ages of 40-55 in the years between 1964 and 1973. Dr. Gilsanz commented on the work, "In our study, we aimed to identify female-specific risks and protective factors impacting brain health, which is critical to diminishing the disproportionate burden of dementia experienced by women."

They found that women with three or more children had a 12 percent lower risk of dementia compared to those having only one child. Miscarriages were associated with an increased risk of dementia and the higher number of miscarriages, the higher the risk. Earlier menopause was also associated with an increased risk of dementia.

The second study was a case control, cross-sectional, which included 133 older women in Britain. The lead researcher was Dr. Molly Fox, assistant professor from the Departments of Anthropology and Psychiatry & Biobehavioral Sciences at University of California, Los Angeles.

The findings showed that the total number of months of pregnancy and those related to the first semester were strongly related to the risk of Alzheimer’s disease. This study found those women who had 12.5 percent more months in pregnancy compared to otherwise similar women had a 20 percent lower risk of having Alzheimer’s disease.

Dr. Fox commented on their findings, "We are intrigued by the possibility that pregnancy may reorganize the mother’s body in ways that could protect her against developing Alzheimer’s later in life. These results also suggest that the story might not be so simple as being all about estrogen exposure, as previous researchers have suggested." One hypothesis is that there may be a residual benefit on the immune system during the early stages of pregnancy.

With the gains in understanding who is at greater risk for having Alzheimer’s disease come increased opportunities to understand prevention and treatment. These findings apply to all at risk for age-related dementias, male and female.