Women who start their period later, go through menopause earlier or have a hysterectomy may have a greater risk of developing dementia, according to a new study published in the March 27, 2019, online issue of Neurology®, the medical journal of the American Academy of Neurology. The study found a link between increased risk of dementia and fewer total reproductive years, during which women are exposed to higher levels of estrogen hormones.
“Since women are 50 percent more likely to develop dementia over their lifetimes than men, it’s important to study any risk factors that are specific to women that could eventually lead us to potential points of intervention,” said study author Paola Gilsanz, ScD, of Kaiser Permanente Division of Research in Oakland, Calif. When looking at total reproductive years, the age of first period to the age of menopause, women who had fewer than 34 years had a 20 percent greater risk of dementia than women who had 34 or more reproductive years.
Of the 1,702 women who had fewer than 34 total reproductive years, 728 later developed dementia, compared to 1,024 of the 2,345 women who entered menopause at age 47 or older. Women who had hysterectomies had an 8 percent greater risk of dementia than those who did not.
Women who had their first menstrual cycle at age 16 or older had a 23 percent greater risk of dementia than women who had their first menstrual cycle at age 13. Of the 258 women who had their first menstrual cycle at age 16 or older, 120 later developed dementia, compared to 511 of the 1,188 women who had their first menstrual cycle at age 13.
Women who went through natural menopause before age 47 had a 19 percent greater risk of dementia than women who went through menopause at age 47 or older. Of the 1,645 women who entered menopause at 47 or younger, 700 later developed dementia, compared to 1,052 of the 2,402 women who entered menopause at age 47 or older.
The researchers studied 6,137 women, members of Kaiser Permanente in Northern California, who completed health surveys and had medical exams. Participants were asked when they had their first menstrual cycle, when they went through menopause and if they had a hysterectomy. Gilsanz and her colleagues then calculated the number of reproductive years for each participant. Researchers used electronic medical records to determine which participants received a diagnosis of dementia later in life.
The researchers adjusted for other factors that could affect a woman’s risk of dementia, including smoking, diabetes, and high blood pressure.
“Estrogen levels can go up and down throughout a woman’s lifetime.”
“Our results show that less exposure to estrogen over the course of a lifetime is linked to an increased risk of dementia. However, while our study was large, we did not have enough data to account for other factors that could affect estrogen levels, like pregnancies, hormone replacement therapy or birth control, so more research is needed,” said Gilsanz.
Further research is needed to understand the biological mechanisms linking aspects of women’s reproductive history and dementia risk.
The study was supported by the National Institute on Aging.
-Adapted from a Neurology news release