Why the FDA's hormone therapy and Alzheimer's claim is only half the story
Why the FDA's hormone therapy and Alzheimer's claim is only half the story
A 1996 study of nearly 9,000 women found that estrogen users had a 35 percent lower risk of Alzheimer disease than women who never used it. The FDA cited that same figure in November 2025 as part of its case for removing the dementia warning from hormone therapy labels. A national registry study of more than 61,000 women, published in 2023, found the opposite: a 24 percent higher risk of dementia and Alzheimer's in women who started hormone therapy, even when they started close to menopause.
Estrogen acts on receptors throughout the brain, including regions tied to memory and reasoning, and researchers have long debated whether that role protects the aging brain or complicates it depending on when a woman starts treatment. The two studies above were run decades apart, on different populations, with different designs, which is part of why they point in opposite directions.
This article explains what the 1996 and 2023 studies each found, why the Women's Health Initiative Memory Study complicates both of them, and what the current evidence supports for a woman weighing cognitive protection against the rest of the hormone therapy decision.
- The 1996 study behind the FDA's Alzheimer's figure
- What newer research adds, and complicates
- Why estrogen affects brain aging in the first place
- Comparing what the research says by starting age and approach
- How Botavive Clarity supports cognitive health during menopause
- Frequently asked questions
| Research | What it found |
|---|---|
| 1996 case control study, 8,877 women | Estrogen users had a 35 percent lower risk of Alzheimer disease, odds ratio 0.65 |
| 2003 WHIMS trial, 4,532 women aged 65 and over | Combined hormone therapy nearly doubled dementia risk, 45 versus 22 cases per 10,000 women per year |
| 2023 Danish registry study, over 61,000 women | Estrogen-progestin users had a 24 percent higher risk of dementia and Alzheimer's, even those who started near menopause |
| FDA's November 2025 position | Cites the 35 percent figure and a 10-year starting window as part of its case for removing the dementia warning |
| Where independent researchers land | Mayo Clinic and Icahn School of Medicine physicians note that none of these observational studies proves hormone therapy causes or prevents dementia |
The 1996 study behind the FDA's Alzheimer's figure
The study the FDA cites was conducted among residents of Leisure World Laguna Hills, a retirement community in Southern California. Researchers Annlia Paganini-Hill and Victor Henderson followed a cohort of 8,877 women starting in 1981, then compared 248 women who died with an Alzheimer's or related dementia diagnosis against five matched controls apiece.
Women who had used estrogen had a 35 percent lower risk of Alzheimer's and related dementia than women who never used it, an odds ratio of 0.65. The effect held for both oral and non-oral estrogen, and it grew stronger with higher doses and longer duration of use. Women who used the highest doses for the longest time had the lowest observed risk in the study.
That 35 percent figure is nearly thirty years old, and it is not the only word on the subject.
What newer research adds, and complicates
The Women's Health Initiative Memory Study, published in 2003, followed 4,532 postmenopausal women aged 65 and older for 4.2 years. Half took combined estrogen and progestin, half took a placebo. The result ran counter to the 1996 finding: 45 women per 10,000 developed dementia each year on hormone therapy, compared with 22 per 10,000 on placebo, close to double the risk. The trial arm was stopped early once researchers concluded the risks outweighed the benefits for that age group.
A 2023 study published in The BMJ complicated the picture further. Danish researchers compared roughly 5,600 women with dementia against nearly 56,000 age-matched women without it, tracking hormone therapy use from age 50 to 60 and following outcomes to an average diagnosis age of 70. Women who used estrogen-progestin therapy had a 24 percent higher risk of all-cause dementia and Alzheimer's, and the risk rose with duration, from 21 percent for a year or less of use to 74 percent for more than 12 years. Unlike WHIMS, this increased risk showed up even among women who started therapy close to menopause, the exact window the FDA's new labeling points to as protective.
| Study | Population | Finding |
|---|---|---|
| 1996 case control study | Retirement community cohort, average age older than typical menopause onset | 35 percent lower Alzheimer's risk among estrogen users |
| WHIMS, 2003 | Women 65 and older | Combined hormone therapy nearly doubled dementia risk |
| Danish registry study, 2023 | Women starting therapy near menopause, followed to average age 70 | 24 percent higher dementia and Alzheimer's risk, rising with duration of use |
- Observational studies like these cannot fully separate the effect of hormone therapy from the underlying health differences between women who choose to use it and women who do not.
- The three studies above used different formulations, doses, and durations of therapy, which makes direct comparison difficult.
- A randomized, placebo-controlled design, the strongest form of evidence, exists only for the WHIMS population of women 65 and older.
Why estrogen affects brain aging in the first place
Estrogen receptors sit throughout the hippocampus and prefrontal cortex, the regions most involved in memory and reasoning. Estrogen also supports how brain cells use glucose for fuel and has antioxidant properties that researchers believe help protect neurons from the kind of damage that accumulates with age.
The critical window hypothesis
Researchers use the term critical window hypothesis to describe the idea that estrogen's effect on the brain depends heavily on timing. Starting therapy while brain tissue is still responsive to estrogen, closer to menopause onset, appears to work differently than introducing it after years without estrogen exposure, once vascular and cellular changes have already taken hold. The 2023 Danish study is part of why this hypothesis is no longer treated as settled.
Supplement-based cognitive support
Outside of hormone therapy, several nutrients have research behind their role in memory and focus during midlife. DHA supports neuronal membrane structure, Bacopa and Ginkgo Biloba have been studied for memory and processing speed, L-Theanine and GABA support calm focus, and phosphatidylserine is involved in the signaling that keeps brain cells communicating efficiently.
Pro Tip: If cognitive protection is the main reason you are considering hormone therapy, that reason alone should not settle the decision. Ask your prescriber which study population your age and starting window resemble, since the FDA's updated label reflects one strand of the evidence, not all of it.
Comparing what the research says by starting age and approach
Four paths sit in front of a woman weighing hormone therapy against cognitive risk: starting within the FDA's recommended window, starting later, skipping hormone therapy, or layering in non-hormonal support regardless of which of the first three she chooses.
| Approach | Pros | Considerations | Best for |
|---|---|---|---|
| Starting HRT within 10 years of menopause onset | Aligns with the FDA's updated labeling and the 1996 study population | The 2023 Danish study found increased risk even in this window | Women without contraindications who want a full risk discussion with a doctor |
| Starting HRT after age 65 | Addresses menopause symptoms that persist later in life | WHIMS found nearly double the dementia risk in this group | Women with a specific medical reason, discussed individually |
| Declining hormone therapy | Avoids the endometrial cancer warning and this entire debate | Menopause symptoms go unaddressed without another treatment | Women with contraindications or a strong preference against hormones |
| Non-hormonal cognitive support | No hormone exposure, supports general brain health | Evidence is more modest than the effects reported for hormone therapy in either direction | Women who want foundational support regardless of their HRT decision |
None of these four paths cancel each other out. A woman who starts hormone therapy for hot flashes still benefits from adding nutrient-based cognitive support, and a woman who declines hormone therapy entirely still benefits from the same foundational habits, sleep, movement, and specific nutrients tied to memory function.
Know when to seek professional evaluation:
- A family history of dementia or Alzheimer's disease
- A personal history of stroke, blood clots, or breast cancer
- Memory changes that concern you or the people around you
- Uncertainty about which of the studies above best matches your age and health history
- You are weighing whether to start or stop hormone therapy specifically for cognitive reasons
How Botavive Clarity supports cognitive health during menopause
Brain fog, word-finding trouble, and memory lapses show up during the menopause transition on their own timeline. They do not wait for a woman to settle the hormone therapy and Alzheimer's question, which, as the research above shows, does not have a single settled answer yet.
Botavive Clarity was formulated around that gap. It combines DHA, Bacopa, Ginkgo Biloba, L-Theanine, GABA, Phosphatidylserine, and B vitamins, ingredients studied individually for their role in memory, focus, and calm cognitive function.
Clarity is not a treatment for Alzheimer's disease or dementia, and it does not replace a conversation with a doctor about hormone therapy. It is formulated to give daily cognitive support for a woman to use whether she starts hormone therapy, waits, or decides against it entirely.
Frequently asked questions
Did the FDA's label change include new research on Alzheimer's risk?
The FDA cited a 1996 study that found a 35 percent lower Alzheimer's risk among estrogen users as part of its case for removing the dementia warning. That study predates several newer analyses, including a 2023 Danish registry study that found increased risk, so the FDA's figure represents one part of the evidence rather than a new consensus.
Why do studies on hormone therapy and Alzheimer's disagree with each other?
The studies differ in the age of participants, the hormone formulations used, how long women were followed, and whether the design was observational or a randomized trial. Researchers also note that observational studies cannot fully separate hormone therapy's effect from other health differences between women who choose to use it and women who do not.
Does starting hormone therapy early protect against Alzheimer's disease?
Some research, including the FDA's cited 1996 study, associates earlier starting with lower risk. A 2023 Danish study found increased risk even among women who started near menopause, so the evidence on timing is not settled.
Is hormone therapy ever used specifically to treat memory problems?
No. Hormone therapy is FDA-approved for menopause symptoms such as hot flashes, night sweats, and vulvovaginal changes, not as a treatment for memory loss, dementia, or Alzheimer's disease. Any cognitive effect discussed in the research above is a secondary finding, not an approved use.
What should a woman do for brain health if she is unsure about hormone therapy?
Sleep, regular movement, and nutrients studied for cognitive function, including DHA and B vitamins, all have research behind their role in brain health during menopause and do not require resolving the hormone therapy question first.
Sources
- Paganini-Hill A, Henderson VW, 1996. Estrogen replacement therapy and risk of Alzheimer disease, Archives of Internal Medicine. pubmed.ncbi.nlm.nih.gov
- University at Buffalo, 2003. Coverage of the Women's Health Initiative Memory Study finding that combined hormone therapy nearly doubled dementia risk in women 65 and older. buffalo.edu
- Medical News Today, 2023. Coverage of the Danish registry study finding a 24 percent higher dementia and Alzheimer's risk among hormone therapy users. medicalnewstoday.com
- U.S. Department of Health and Human Services, 2025. Fact sheet on the FDA's removal of black box warnings from menopausal hormone therapy products, including the cited Alzheimer's risk figure. hhs.gov