Researchers Looked at 180,000 Post-Menopausal Women and Found This Surprising Link Between HRT and Dementia

4 min readA new observational study suggests that hormone therapy can help to lower your risk of Alzheimer’s disease by up to 26 percent. The risk reduction varies depending on personal circumstances. Doctors say more research is needed. Hormone therapy to treat symptoms of menopause has exploded in popularity, with use nearly doubling among some cohorts over the past nine years. While more women are relying on the treatment to ease symptoms like hot flashes and trouble sleeping, research suggests there are even more perks to consider, like better bone density. Now, there’s one more potential benefit to add to the list: a possible lower risk of dementia.That’s the major takeaway from new research published in the journal Alzheimer’s & Dementia. But it’s important to stress this upfront: The study didn’t prove that using hormone therapy will magically make your risk of dementia disappear—instead, it just found that women who used hormone therapy were less likely to have dementia. Doctors also note that something else may be happening behind the scenes to explain this.Women in general are more likely to develop dementia compared to men, simply because they tend to live longer, says Clifford Segil, DO, a neurologist at Providence Saint John's Health Center in Santa Monica, California. But there may be more to the story than that, he says.If you’re already considering using hormone therapy, it’s more than fair to want to know a little more. Here’s what the research uncovered, plus what could be fueling this.Meet the experts: Lauren Streicher, M.D., a clinical professor of obstetrics and gynecology at Northwestern University Feinberg School of Medicine and host of Dr. Streicher's Inside Information: Menopause, Midlife, and More podcast; Clifford Segil, DO, a neurologist at Providence Saint John's Health Center in Santa Monica, California.What did the study find?For the study, researchers followed 183,450 postmenopausal women for about 13 years who participated in the UK Biobank, a large-scale biomedical database. During that time, nearly 4,000 women were diagnosed with dementia. The scientists then further analyzed whether using hormone therapy could be associated with risk factors.The researchers discovered that women who went through early menopause or started their periods late had the biggest benefit compared to those who didn’t use hormone therapy, with a 16 percent lower risk of developing any form of dementia. They also found that women who carried the APOE4 genetic variant (linked to a higher risk of dementia) saw a benefit, though it was not considered statistically significant.The biggest drop in risk was in women who went through surgical menopause—they saw their risk decrease by 26 percent.Overall, when compared to women who didn’t use hormone therapy, those who used the treatment were 10 percent less likely to be diagnosed with any form of dementia and 16 percent less likely to be diagnosed with Alzheimer’s disease.“These findings may help inform more tailored approaches to hormone replacement therapy prescribing in relation to women's lifetime dementia risk,” the researchers wrote in the study.Why might hormone therapy lower Alzheimer’s risk?Again, this study simply found a link between using hormone therapy and lower odds of being diagnosed with dementia—it didn’t prove that hormone therapy prevents dementia. But experts have a few theories as to what may be behind this.“Women taking hormone replacement therapy often feel better with these types of treatments,” Dr. Segil says. It’s possible that translates to more brain-healthy behaviors like being physically active and sleeping better, but he stresses that the real reason for this link is “unknown.”Lauren Streicher, M.D., a clinical professor of obstetrics and gynecology at Northwestern University Feinberg School of Medicine and host of Dr. Streicher's Inside Information: Menopause, Midlife, and More podcast, also says more research is needed. “The results are likely due to healthy user bias,” she says. Meaning, women who choose to use hormone therapy or who have access to it are healthier and already have a lower baseline risk of dementia.However, this isn’t the only research to find a link between hormone therapy and a lower risk of dementia. A meta-analysis of 50 clinical trials and observational studies presented last year found that women who started hormone therapy within five years of menopause had a 32 percent lower risk of developing Alzheimer’s disease. However, those who started hormone therapy at age 65 or older had a 38 percent higher risk of developing Alzheimer’s disease. (There’s a "critical window" theory that suggests starting hormone therapy soon after menopause may be good for the brain, but starting after 65 could be bad for the brain.)What’s the takeaway?It’s tough to say at this point. “Hormone replacement therapy is a reasonable treatment for menopause symptoms,” Dr. Segil says, adding that “current trends show hormone replacement therapy being used with more benefits for brain health, overall wellbeing, and maybe longevity.”But Dr. Streicher stresses that we’re not there yet with recommending hormone therapy purely to lower your risk of dementia. “This is not an indication that post-menopause estrogen will decrease the likelihood of developing dementia,” she says.Carina Hsieh, MPH, is the deputy features editor of Women’s Health. She has more than a decade’s worth of experience working in media and has covered everything from beauty, fashion, travel, lifestyle, pets, to health. She began her career as an intern in the fashion closet at Cosmopolitan where she worked her way up to Senior Sex & Relationships Editor. While covering women’s health there, she discovered her passion for health service journalism and took a break to get her Masters in Public Health. Post-grad school, she worked as a freelance writer and as The Daily Beast’s first Beauty, Health, and Wellness Reporter. Carina is an alum of the Fashion Institute of Technology and the Yale School of Public Health. She and her French Bulldog, Bao Bao, split their time between Brooklyn and Connecticut. She enjoys reformer Pilates, (slow) running, and smelling the fancy toiletries in boutique fitness class locker rooms.