You’ve probably heard some version of “HRT protects the brain,” but the science tells a more complicated story. This week we dive into the study that started a women’s health scare and the most recent data from the 2026 Cambridge Study on how hormones impact our cognitive function, including the risk of Alzheimer's.
🧠 The takeaway
HRT may support brain health, but only if started at the right time.
A major 2026 Cambridge/UK Biobank study found that HRT slows some cognitive changes but does not prevent the loss of brain tissue linked to Alzheimer’s disease.
The question isn’t “will HRT protect my brain?” The better question is: am I on the right formulation, at the right time, for my individual risk profile?
⚕️ Hormone therapy isn't a yes or no question. It's a timeline. Read more about how the risks, benefits, and clinical decisions shift across the decades.
The study that scared everyone
For years, the Women’s Health Initiative Memory Study (WHIMS) cast a long shadow over HRT, including its impact on brain health. The study’s finding was that estrogen plus progestin given to women was associated with increased dementia risk, not protection.
But, WHIMS studied women who were already in their mid-to-late sixties, many years past menopause. As Sundus Amena, a GMC-registered gynecologist specializing in hormonal health, explains: “Healthy neurons in early years respond better to estrogen, while hormones cause neurotoxic insult to already neurodegenerated neurons.”
In other words, you have to consider the current state of your cognitive health to determine the potential benefits of HRT.
The timing hypothesis: when you start may matter more than whether you start
Two major trials (ELITE and KEEPS) looked at women who began HRT within ten years of menopause or before age 60. Their findings were notably different from WHIMS:
Starting HRT early doesn't seem to harm brain function, and it may actually help protect against dementia by keeping the brain's blood vessels healthy.
It appears that the brain is most responsive to estrogen when neurons are still healthy (a similar finding exists across all organs). The underlying mechanism here is sometimes called the “critical window hypothesis.” Start early, and estrogen has something to work with. Start later, when vascular changes, inflammation, or early neurodegeneration may already be underway, and the picture might change.
As Dr. Betsy Greenleaf, a board-certified physician specializing in menopause, says: “The brain’s response to hormone therapy may depend on when treatment is initiated, the formulation used, underlying vascular and metabolic health, and the individual’s genetic risk factors.” It’s not a one-size-fits-all solution.
What the 2026 Cambridge study found
Earlier this year, a large observational study using UK Biobank data added an important layer to this conversation. Researchers found that menopause was associated with measurable differences in brain structure, mental health, sleep, and cognitive function. Women who had used HRT showed some improvements in certain measures, but HRT did not appear to fully offset all of the changes associated with menopause.
Specifically, as Amena notes, the study found that while early HRT “successfully slows down senile psychomotor changes, it does not prevent the actual loss of grey matter in the hippocampus, which is the basis of Alzheimer’s disease.”
The British Menopause Society has said that HRT is not a tool for dementia prevention. But that doesn’t mean it has no role in brain health. It means the role is more targeted and more conditional than the popular narrative suggests.
Formulation matters too
One thing both researchers and clinicians agree on: Not all HRT is the same, and the delivery method matters. When estrogen is taken as a pill, it passes through the liver first, which reduces how much actually reaches the brain. The patch or gel skips that process entirely, delivering estrogen more directly. That's why many doctors now prefer the patch or gel over the pill, especially for women with heart or circulation concerns as it also carries a lower clotting risk.
There’s a difference between taking estrogen alone versus combining it with progestogen. (If you have a uterus these two prescriptions should always come together.) And even the specific type of progestogen can affect your personal risk picture. These are distinctions your provider should walk you through, not assumptions baked into a generic prescription.
Menopause is a brain event, not just an ovarian one
Perhaps the most useful reframe in this conversation is one that often gets skipped entirely: estrogen, progesterone, and testosterone interact with neurotransmitter systems (serotonin, dopamine, GABA, acetylcholine) that govern mood, memory, sleep, stress resilience, and pain.
This helps explain why so many women experience cognitive symptoms during the menopausal transition that get dismissed as “getting older.” They may be getting older, but what’s happening in the brain during this window is more specific than that. As Greenleaf puts it, “Menopause is not just an ovarian event — it is a brain event.”
The questions worth asking
If you’re on HRT, thinking about starting it, or wondering whether your current approach is right for your brain health, here’s a more useful framework than “is HRT protective?”
Am I an appropriate candidate based on my age, time since menopause, and medical history?
What route and formulation is right for my individual cardiovascular and metabolic profile?
What are my personal risk factors (cardiovascular, breast cancer, and dementia history in my family)?
What else am I doing for brain health? (Sleep, strength training, blood sugar regulation, stress, and social connection all matter here, too.)
Hormones are just one piece of the brain-health puzzle, not the entirety of good brain health. The more we know, the better better we can help our brains function well for our lifetimes.
Are you worried about your brain health?
Navigating Women’s Healthcare
You know the science. You've done the research. You've even come to the appointments prepared. And still, you leave the doctor's office without what you needed.
For women, navigating the healthcare system isn't just frustrating. It can feel like a full-time job that nobody trained you for.
Join Rebecca Bloom in the Livelong Women's Circle tomorrow, June 11, for a live conversation on exactly this. We'll cover how to advocate for yourself when the system isn't working for you, and there's dedicated Q&A time at the end, so bring your questions.
More things we recommend
The brain health conversation doesn't stop here. This September in New York City, the Livelong Women's Health Summit brings together the physicians, researchers, and experts who are changing what we know about women's health and aging.
Early bird pricing ends this Friday, June 12th
Use code TIFFANY to save an additional $50.
Become a Livelong Ambassador
If this issue resonated with you, imagine being the person who brings these conversations to the women in your life. Livelong Ambassadors help us reach more women with science-backed health information and get exclusive perks for doing it.
This is the kind of topic our Inner Circle goes deep on. On June 24th, Dr. Amy Day joins us live to answer the HRT questions you actually have — the ones that don't fit in a newsletter. That conversation is for paid members only.
👉 Join the Inner Circle (Use code LLWNEWS for a special rate.)
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👀 In case you missed it:
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The information provided about wellness and health is for general informational and educational purposes only. We are not licensed medical professionals, and the content here should not be considered medical advice. Talk to a doctor before trying any of these suggestions.
