When asking why more women than men have Alzheimer’s disease or dementia – nearly two-thirds of Americans with the disease are women – the prevailing explanation has been that women live longer and that it is a disease associated with aging.
But scientists at the Alzheimer’s Association International Conference in Chicago on Monday said it is important to look at how women’s reproductive history relates to their risk of developing the disease. Their latest research has found associations between a woman’s dementia risk and her number of children, miscarriages, cumulative months of pregnancy and years between first menstrual period and menopause.
In a study of 14,595 long-term Kaiser Permanente members, researchers looked at the reproductive history of women who were 40 to 55 between 1964 and 1973 and were still members between 1996 and 2017.
They found that women who had had three or more children had a 12 percent lower risk of dementia in later life than those with fewer children. The study also showed that women who didn’t get their first period until age 16 or 17 had a 31 percent higher risk of dementia than those who began menstruating at 13, and that women who stopped menstruating at age 45 or earlier had a 28 percent higher risk of dementia than women who stopped menstruating after age 45.
“One hypothesized reason is that it is cumulative exposure to estrogen across the life course,” which may protect against the disease, said Paula Gilsanz, a staff scientist at the division of research at Kaiser Permanente Northern California and an author of the study.
The study, the largest of its kind in the United States, spanned a range of education levels and included 32 percent nonwhite subjects, making it more diverse than many.