Women who used estrogen-only hormone therapy later in life were less likely to develop dementia than those who did not, according to research published August 12, 2026, in Neurology, the medical journal of the American Academy of Neurology. The analysis drew on medical records from two large data sets covering 21,462 female participants, 1,953 of whom had taken hormone therapy.
The researchers deliberately narrowed their focus to estrogen-only therapy, because earlier work has suggested that estrogen combined with progestin may actually raise dementia risk. Participants were followed for roughly three to five years beginning at an average age of 71, and those who took hormone therapy had typically started it after age 70. Beyond clinical testing during life, 728 women in one data set underwent brain scans or biomarker testing, and 2,959 women in the other had autopsies at an average age of 82 to look for the hallmarks of Alzheimer's disease - allowing the team to connect hormone use to physical markers of disease, not just diagnoses.
The timing matters here. Much of the debate over hormone therapy and the brain has centered on when treatment begins, and this study addresses women who started well past menopause, a group often assumed to gain little cognitive benefit. Finding an association with lower dementia risk in that later-starting group gives researchers a reason to keep examining how the timing and formulation of hormone therapy interact with brain aging.
The study's authors were explicit about the limits. The women analyzed were using hormone therapy decades ago, when the timing and type of treatment differed from what most women receive now, so the findings are informative but may not translate to current practice. Estrogen-only therapy today is generally prescribed only to women who have had a hysterectomy, because of endometrial cancer risk. The researchers said more work is needed before any recommendations can be made to women about hormone therapy and brain health.