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Nearly two-thirds of people living with Alzheimer's disease are women. Scientists think sex hormones like estrogen may be one reason for the disparity. NPR's Jon Hamilton reports on research presented today at the Alzheimer's Association International Conference in Chicago.
JON HAMILTON, BYLINE: Women live longer than men, so it's not surprising that they make up the majority of patients with Alzheimer's and other forms of dementia. But Maria Carrillo, chief science officer of the Alzheimer's Association, says there's growing evidence that something else is going on.
MARIA CARRILLO: It isn't just that women are living longer, right? There is some biological underpinning. And because of the large numbers of women that are affected, it's important to find out.
HAMILTON: One possible explanation involves hormones, like estrogen. And several studies presented at this year's Alzheimer's Conference support that idea. One of the studies looked at nearly 15,000 women in California. Carrillo says the research found a link between a woman's reproductive history and her risk of memory problems later in life.
CARRILLO: For example, women who have more than three children may have decreased risk of dementia.
HAMILTON: The risk for these women was 12 percent lower than for women who had only one child. On the other hand, the risk for women who'd experienced early menopause was nearly 28 percent higher. Both findings suggest that estrogen, which rises during pregnancy and falls at menopause, may help protect women from dementia. Pauline Maki, a professor of psychiatry and psychology at the University of Illinois at Chicago, says it's not just that women have more estrogen than men.
PAULINE MAKI: Women experience these very dramatic hormonal transitions that in the long run can give rise to Alzheimer's disease.
HAMILTON: One way for women to minimize the hormonal changes at menopause is to take estrogen. That approach fell out of favor more than a decade ago when a large study found that women who took hormones after menopause were actually more likely to get some form of dementia. They also seemed to have a higher risk of heart disease and breast cancer. But Maki says more recent studies have found that hormones really can help prevent dementia if women get them at the right time.
MAKI: The effects of hormone therapy depend on the timing of use. Use later in life is detrimental, whereas use early in the menopausal transition could be beneficial.
HAMILTON: An analysis presented at the meeting supports that idea. It found that in two different studies, women who took hormones in their 60s and 70s were more likely to have trouble with thinking and memory. But women who took hormones only during their early 50s had no increase in risk. Maki says estrogen may benefit younger women because it reduces the hot flashes associated with menopause. She says her own research has found that these hot flashes are bad for the brain.
MAKI: The more hot flashes a woman has, the worse her memory performance. And when we intervene to address those hot flashes, her memory performance bounces back.
HAMILTON: Maki says findings like that are renewing interest in the idea of using hormones to prevent Alzheimer's and other forms of dementia. Jon Hamilton, NPR News.
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