Timing of Hormone Replacement Therapy Key to Alzheimer's Disease Risk

Recent research presented at the 150th Annual Meeting of the American Neurological Association highlights the significant impact that the timing of hormone replacement therapy (HRT) may have on a woman's risk of developing Alzheimer’s disease. The study emphasizes that initiating HRT within five years of menopause could decrease the risk of Alzheimer’s by up to 32%. Conversely, delaying treatment until age 65 or later may increase the risk by approximately 38%.

In an extensive meta-analysis of over 50 clinical trials and observational studies, scientists explored how the timing of hormone therapy influences both the occurrence and progression of Alzheimer’s, as well as related brain changes observable through scans and laboratory tests. Naturally, estrogen levels drop significantly after menopause; HRT helps maintain estrogen's protective effects on brain cells, facilitating communication between neurons, reducing inflammation, and shielding against neurodegenerative damage.

However, the research suggests that starting HRT too late—after prolonged estrogen deficiency—may actually worsen brain inflammation or vascular stress, especially if early signs of Alzheimer’s are already present, such as protein build-up or reduced blood flow. Dr. Vaibhav, a researcher from India, explains that early intervention can be akin to watering a young plant, offering protection during its growth phase. But if degenerative changes are already underway, HRT might offer limited benefit or even pose risks.

The types of HRT vary, including estrogen alone, estrogen combined with progestin, or with selective estrogen receptor modulators, administered via pills or patches. Typically used to alleviate menopause symptoms and protect heart and bone health, HRT is currently used by less than 5% of American women, a decline from nearly 26% in 1999.

This comprehensive analysis indicates that women who begin hormone therapy close to menopause are less likely to develop Alzheimer’s later in life, whereas starting later may increase risks, especially with progestin-inclusive therapy. Dr. Vaibhav recommends that women consult with healthcare providers about the timing and duration of HRT, emphasizing that delaying or initiating therapy in older age might be counterproductive. It’s advised that hormone therapy should primarily be aimed at managing menopausal symptoms, and initiating treatment early may confer neurological benefits.

[Source: https://medicalxpress.com/news/2025-09-hormone-therapy-alzheimer-disease.html]