Dr. Heidi Queen, MD | Energize Health & Hormones

For years, the relationship between estrogen therapy and the aging brain has been anything but simple. Now, new research is adding another intriguing piece to the puzzle: women who had used estrogen-only hormone therapy later in life were less likely to have dementia and showed fewer signs of Alzheimer’s disease in their brains.

The study, published August 12, 2026, in Neurology, analyzed data from more than 21,000 women. Researchers found that women who had used hormone therapy had lower odds of receiving a dementia diagnosis and were also less likely to show Alzheimer’s-related changes in brain tissue after death. That sounds encouraging — but it is important to understand what the study does and does not tell us.

What did the new study actually find?

Researchers combined information from two large groups of women. One included women who underwent brain scans or biomarker testing during life, while the other included women whose brains were examined after death for evidence of Alzheimer’s disease. The analysis focused specifically on estrogen-only hormone therapy. Among the women whose brains were examined after death, 18% of those who had used hormone therapy showed no signs of Alzheimer’s disease, compared with 10% of women who had not used hormone therapy.

At the other end of the spectrum, 40% of hormone therapy users showed all three major Alzheimer’s-related features researchers were looking for — amyloid-beta plaques, tau tangles and neuritic plaques — compared with 51% of women who had not used hormone therapy. After accounting for factors including age, education, genetics, race and hypertension, hormone therapy use was associated with 35% lower odds of showing Alzheimer’s-related pathology at autopsy.

The researchers also found that women who had used hormone therapy had biomarker levels consistent with less amyloid accumulation in the brain and had 39% lower odds of receiving a clinical dementia diagnosis. They were also less likely to show problems with memory or everyday functioning. Those are significant findings. But there is an important catch.

Does this mean estrogen prevents dementia?

No — and the researchers themselves emphasize this point. This was an observational analysis, meaning researchers looked at associations between past hormone therapy use and later outcomes. It cannot establish that estrogen therapy caused the lower dementia risk.

There is another important limitation: the women in this study generally started hormone therapy much later than women typically do today. The average age at which hormone therapy users began treatment was over 70, while current practice generally involves considering hormone therapy during the menopausal transition or early post menopause, often in the late 40s or early 50s.

As study author Jennifer Bruno, PhD, noted, the timing and type of hormone therapy used by these women differed from current practice. The results are therefore informative, but they may not directly apply to today’s hormone therapy approaches. That distinction is especially important when talking about hormone therapy and brain health.

Why does estrogen matter to the brain in the first place?

Estradiol is one of the body’s primary forms of estrogen, and its effects extend well beyond reproductive health. Estrogen plays roles in bone health, skin integrity, mood and other systemic processes. During menopause, estradiol production declines substantially. For some women, that hormonal shift is accompanied by hot flashes, night sweats, sleep disruption, mood changes, vaginal symptoms, changes in libido and the frustrating experience commonly described as “brain fog.”

That doesn’t mean every symptom is caused by estrogen deficiency alone, nor does it mean hormone therapy is appropriate for every woman. It does, however, help explain why researchers continue to investigate estrogen’s effects throughout the body — including the cardiovascular system, bones and brain.

Is the way estrogen is delivered important?

It can be. Estradiol is available in several forms, including oral medications, transdermal patches, topical gels and creams, and other delivery systems. Transdermal estradiol, such as an estrogen patch, delivers estradiol through the skin and into the bloodstream rather than passing first through the gastrointestinal tract and liver.

This route may offer some advantages compared with oral estrogen, including more stable hormone delivery and potentially lower risk of certain clotting-related effects. The choice of therapy, however, depends on the individual’s health history, symptoms, risk factors, preferences and treatment goals. And there is an important distinction between estrogen-only therapy and combined estrogen-progestogen therapy.

Why isn’t everyone prescribed estrogen alone?

For women who have a uterus, estrogen therapy is generally combined with a progestogen to help protect the endometrium, or uterine lining. Estrogen-only therapy is generally used in women who have undergone a hysterectomy because unopposed estrogen can increase the risk of endometrial cancer.

That means the encouraging findings from this particular study should not be interpreted as evidence that every woman should take estrogen alone. The study examined a specific type of hormone therapy in a particular population.

What should we take away from this research?

Perhaps the most useful takeaway is that our understanding of estrogen and healthy aging continues to evolve. The new research adds to a growing body of evidence suggesting that estrogen may have effects on the brain that deserve further investigation. At the same time, it does not establish hormone therapy as a treatment for preventing dementia or Alzheimer’s disease.

For women considering hormone therapy, the conversation should therefore be much broader than a simple question of whether hormones are “good” or “bad.” The more useful questions are: When is therapy being started? What symptoms or health concerns are being addressed? Which formulation and route of delivery make sense? What are the individual’s cardiovascular, cancer and clotting risks? And how do the potential benefits compare with the potential risks over time?

Hormone therapy is not one-size-fits-all. It is a medical decision that should be individualized and revisited as a woman’s health and needs change. And as research continues to explore the relationship between estrogen, menopause and brain health, we may learn considerably more about how the timing, formulation and duration of hormone therapy influence healthy aging.

Looking at the whole picture

At Energize Health & Hormones, Dr. Queen takes an individualized approach to women’s health and hormone care, considering symptoms, medical history, risk factors and personal health goals when evaluating whether hormone therapy may be appropriate.

If you’re wondering whether hormone therapy might be right for you — or simply want a more informed conversation about menopause, estrogen and healthy aging — personalized medical guidance can help you understand your options and make decisions based on your own health picture. Call  (415) 548-7901 to learn more about working with Dr. Queen.