Women are about twice as likely as men to develop Alzheimer's disease, yet decades of research on whether menopausal hormone therapy (MHT) protects or harms the brain have produced conflicting answers. A study published August 12 in Neurology now brings the debate down to the tissue itself: the first large analysis to link MHT use to Alzheimer's hallmark pathology in autopsied brains.
Stanford Medicine researchers led by neuroscientist Hadi Hosseini examined two existing databases covering 21,462 participants, comparing 258 brains of women who had used estrogen-only therapy with about 2,701 brains of women who never used MHT. They scored the brains for the disease's defining features: amyloid plaques, tau-based neurofibrillary tangles and neuritic plaques.
Estrogen-only users showed a statistically significant 35% reduction in the odds of severe Alzheimer's pathology — a result mirrored in life: users had 39% lower odds of a clinical dementia diagnosis, plus better scores on memory tests and independent functioning. Because estrogen-only therapy is normally prescribed to women without a uterus, most users had had hysterectomies.
The finding applies only to oral estrogen-only regimens, not estrogen-plus-progestin combinations or topical forms, and the authors stress it is an association, not proof of causation. But it runs against the prevailing caution triggered by the 2003 Women's Health Initiative Memory Study, which linked combination therapy to higher dementia risk and sent lifetime MHT use from roughly 27% of women down to under 5%. 'This study flies in the face of that recommendation,' says co-lead author Jennifer Bruno. The team says the results should spur clinical trials tracking biomarkers from the start of menopause onward.
