Could Treating Menopause Early Help Prevent Alzheimer's in Women?

Scientists have long wondered why women are more likely to get Alzheimer's disease than men. Two new studies published this week offer some important clues. Researchers found that a natural change in women's bodies, called menopause, may play a big role in brain health. The studies suggest that treating menopause early with hormone therapy could lower a woman's risk of developing dementia.

Menopause happens when a woman's body stops producing as much of a hormone called estrogen. This usually occurs in a woman's late 40s or early 50s. Scientists think the sudden drop in estrogen might affect the brain in ways that could lead to Alzheimer's disease over time. Understanding this connection is a key step toward finding ways to protect women's brain health.

The first study looked at more than 180,000 women in the United Kingdom who had already gone through menopause. Researchers found that women who used hormone replacement therapy, also called HRT, had a 10 percent lower chance of getting any kind of dementia. They also had a 16 percent lower chance of getting Alzheimer's disease specifically. These results held up even after scientists accounted for things like smoking, education level, and ethnicity.

Some women go through menopause because of surgery, such as having their uterus or ovaries removed. For this group, the benefits of HRT were even stronger — their risk of dementia dropped by 26 percent. Women who started HRT at younger ages, between 46 and 56 years old, had a lower risk than those who waited until later to begin treatment. This points to the idea that starting treatment sooner may make a bigger difference for the brain.

Anne-Marie Minihane, a professor at the University of East Anglia in England and the lead senior author of that study, called it the 'most comprehensive analysis in this space to date.' She was careful to point out, though, that this study is not a clinical trial. That means scientists cannot yet say for certain that HRT directly protects against Alzheimer's. What they can say is that there is a strong connection between hormone treatment and lower dementia risk.

The second study, published in the journal JAMA Network Open, looked at when menopause begins and how that timing affects the brain. It found that women who experienced menopause at a younger age were more likely to show signs of cognitive decline, meaning their thinking and memory skills got worse, earlier in life. They were also more likely to be diagnosed with Alzheimer's disease at a younger age. Again, the results were especially strong in women who had surgical menopause.

That second study also found something surprising about brain tissue. Women who had earlier menopause were more likely to develop damage to an area of the brain called white matter. This kind of damage can be a sign that the brain is not as healthy as it should be. Interestingly, this particular finding was more common in women who went through natural menopause, not surgical menopause.

Riley Bove, a professor of neurology at the University of California, San Francisco, was a senior author on the JAMA Network Open study. She said researchers already knew that earlier menopause was linked to a higher risk of cognitive decline. But her study added something new — it showed that menopause leaves a lasting mark on the brain that scientists can still detect many decades later. That finding helps explain why some women may face greater brain health challenges as they age.

Researchers think estrogen may be the key ingredient that helps protect the brain. Women who have surgical menopause tend to have fewer years of estrogen in their bodies, which could partly explain their higher risk. Some earlier research also found that taking estrogen-only HRT, rather than a combination of hormones, was linked to a lower risk of Alzheimer's disease. These details are helping scientists piece together how hormones and brain health are connected.

However, experts are careful to say the picture is not completely clear yet. Some past studies found that combined hormone therapy actually raised the risk of dementia in women over 65. Other studies found little to no effect from taking HRT at all. Scientists are still working to understand why the results from different studies don't always match up.

Both Minihane and Bove say the research supports the idea of a 'window of opportunity' — a period earlier in life when acting quickly might help protect the brain. Minihane hopes to run a full clinical trial to test how HRT affects Alzheimer's more directly. She also wants to study whether certain foods, like soybeans, which contain plant-based estrogens called phytoestrogens, might help support brain health. 'We have a long way to go,' Minihane said, but added that one day HRT might be recommended to help reduce the lifetime risk of dementia.