In 2023 a large nationwide study published in BMJ made a lot of women very worried about their brains. The headline: women who had used hormone therapy had higher rates of dementia compared to women who had not, even when therapy was started before age 55. If you saw that headline and quietly panicked, I want you to understand exactly what that study did and did not show, because the nuance here matters enormously. And because the knee-jerk interpretation, the one that made it onto social media and into worried patient messages, is not the whole picture.
What the Study Found and What It Did Not Prove
The 2023 BMJ study was observational. It tracked health records across a large population and looked at who developed dementia and who had used hormone therapy. That kind of study is extraordinarily useful for identifying patterns, but it cannot establish causation. The authors themselves noted substantial residual confounding as a concern. What that means in plain language: there are likely systematic differences between women who were prescribed hormone therapy and women who were not, differences that also affect dementia risk. Women who seek out hormone therapy may do so because they are already experiencing cognitive symptoms, brain fog, or sleep disturbances, which are themselves early markers of neurological vulnerability. If that is the case, the association between HRT use and dementia in the data may not be telling us that HRT caused dementia. It may be telling us that women with underlying neurological predispositions were more likely to be prescribed hormone therapy. This is called confounding by indication, and it is one of the most common sources of misleading results in observational pharmacological research.
What the Rest of the Evidence Says
The broader body of evidence on estrogen and the brain does not point in the same direction as the 2023 headline. Estrogen is neuroprotective. It supports glucose metabolism in the brain, reduces inflammation, and promotes synaptic plasticity. Women with premature ovarian insufficiency or who undergo surgical menopause before natural age have consistently higher rates of cognitive decline and dementia risk, which improves significantly with hormone therapy. The timing hypothesis, which I discussed in the context of cardiovascular research, applies equally to the brain. Estrogen initiated during the window of perimenopausal transition appears to support brain health in ways that late initiation, after years of estrogen deprivation, does not. Some researchers use the term healthy cell bias to describe this: estrogen protects healthy neurons, but in already-damaged tissue it may not have the same effect or could even be counterproductive. Ongoing cardiovascular research also argues for early HRT benefits on vascular health, which is directly relevant to vascular dementia risk. Vascular disease is one of the major contributors to cognitive decline.
How I Think About This With My Patients
I do not dismiss the 2023 BMJ study. It is a large, serious piece of research from a credible journal and it deserves to be part of the conversation. What I do not do is treat it as a verdict. The way I frame this with patients is to look at the complete picture. If you are in your late 40s or early 50s, experiencing perimenopause, with no history of dementia in your family, the evidence for hormone therapy protecting your brain is stronger than the evidence against it, particularly with appropriate timing and formulation. If you have a strong family history of Alzheimer's disease, surgical menopause, or premature ovarian insufficiency, hormone therapy may be one of the most important interventions for your long-term cognitive health. The research in those populations is particularly compelling. If you are an older woman starting therapy late with pre-existing cognitive vulnerability, the calculation is different and deserves careful individualized review.
The Bottom Line
One observational study, even a large one, does not overturn the broader mechanistic and clinical evidence base for estrogen's role in brain health. What it does is add a piece to a complicated puzzle. Your brain deserves a nuanced conversation, not a headline-driven refusal. If your doctor cited that BMJ study and told you to stop your hormones without walking through the full evidence base with you, you deserve a second opinion.
Frequently Asked Questions
Should I stop hormone therapy because of the 2023 dementia study? No, not based on that study alone. It is observational, the authors themselves highlight residual confounding as a concern, and it does not align with the broader body of mechanistic and clinical evidence on estrogen and neuroprotection. Talk to a menopause specialist before making changes based on a single headline. Does early timing of hormone therapy matter for brain health? Yes. The timing hypothesis applies to the brain as it does to the heart. Estrogen initiated during or close to the menopausal transition appears to confer different neurological effects than estrogen started many years after menopause in already-depleted tissue. I had a surgical menopause. Does that change my dementia risk? Yes. Women who undergo bilateral oophorectomy before natural menopause have significantly elevated risk of cognitive decline and dementia, and hormone therapy in that population is associated with meaningful risk reduction. This is one of the clearest cases for hormone therapy in the brain health context. What if I have a family history of Alzheimer's disease? A family history is precisely the situation where an individualized, in-depth conversation with a menopause specialist is most important. The evidence for early hormone therapy and cognitive protection in genetically predisposed women deserves serious consideration. If you are ready to get individualized care that reflects where the science actually is, book a complimentary discovery call at doctoranat.com. No pressure, no commitment. Just a real conversation about where you are and what is possible. Book your complimentary discovery call at doctoranat.com Dr. Anat Sapan is a board-certified OB-GYN and menopause specialist, exclusively focused on personalized bioidentical hormone therapy for women in their 40s, 50s, 60s, and beyond. She serves patients via telemedicine in California, Florida, New York, and Illinois.
Anat Sapan, MD
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