Link: https://thesciverse.org/for-20-years-women-were-warned-that-hormone-therapy-raised-their-dementia-risk-a-study-of-21000-women-just-looked-inside-their-autopsied-brains-and-found-the-opposite/

In July 2002, the Women’s Health Initiative trial published interim results showing that combined hormone therapy, estrogen plus progestin, was associated with elevated risks of breast cancer, cardiovascular events, and what the researchers called probable dementia. Within months, hormone therapy prescriptions collapsed. Women already using it stopped. Women considering it were advised against it. The FDA added black-box warnings to hormone therapy labeling citing the dementia risk. For the next two decades, those warnings shaped how millions of women and their doctors approached one of the most common interventions in menopause care.

The scientific foundation for that guidance has since been significantly eroded. Researchers identified multiple problems with the original WHI findings: the average participant was 63 years old, more than a decade past natural menopause, an age at which estrogen’s relationship with the brain may be fundamentally different from its effects in early menopause. The cognitive harms observed in the trial were concentrated in the combined estrogen-progestin group, not the estrogen-only group, which showed a statistical trend toward fewer dementia diagnoses. And the women in the trial were generally older, already symptomatic, and not representative of the population most likely to consider hormone therapy today.

Despite this erosion, the warnings persisted. The FDA did not remove the black-box dementia warnings from hormone therapy products until February 2026, following a comprehensive scientific review and expert panel process that took more than a year.

Now a study from Stanford Medicine has provided the most direct biological evidence yet on one side of this question. Published August 12, 2026 in Neurology, the medical journal of the American Academy of Neurology, it is the first study to measure the connection between estrogen-only menopausal hormone therapy and the physical deposits that define Alzheimer’s disease in autopsied human brains, at a scale large enough to draw meaningful conclusions.

The findings run in the opposite direction from the warnings that shaped two decades of clinical practice.

It'd be interesting to know why the warnings were put on all hormone therapies when the first study only focused on estrogen-progestin.