Starting menopausal hormone replacement therapy (HRT or MHT) in the years around the final menstrual period appears to lower risks of cardiovascular disease, fractures, and overall mortality in appropriately selected women, while starting it a decade or more after menopause is linked with higher risks and fewer benefits. This “timing hypothesis” is now central to updated guidance, but the evidence on brain health is mixed, so early MHT is not recommended solely to prevent dementia.
A large body of randomized trials and meta-analyses now supports the idea that when HRT is started, it matters as much as if it is started at all. When initiated before age 60 and within about 10 years of menopause, MHT is associated with lower all-cause mortality and fewer cardiovascular events compared with no therapy. In contrast, the same drugs started later are linked to more strokes and clotting complications. A recent cardiology review notes that absolute risks of adverse cardiovascular events after starting MHT are substantially lower in women 50–59 or within 10 years of menopause onset than in older women or those further from menopause.
Reanalyses of the Women’s Health Initiative (WHI) and other trials show that women who began HRT near menopause had reductions in coronary events and overall cardiovascular disease, while those starting more than 10 years after menopause saw neutral or harmful effects, particularly more strokes. A classic paper on the timing hypothesis reported that HRT begun before age 60 or within 10 years of menopause significantly reduced all-cause mortality and cardiovascular disease, whereas late initiation did not. Newer consensus statements from cardiology and menopause experts emphasize using transdermal routes and the lowest effective dose in women with low-to-moderate baseline cardiovascular risk early in the transition.
Beyond heart disease, early MHT clearly reduces fracture risk by preserving bone mineral density during the years of fastest postmenopausal bone loss. A combined analysis of 25,389 women from the WHI hormone trials found that MHT reduced fractures regardless of baseline fracture probability or history of falls, suggesting a broadly protective skeletal effect. Reviews also note favorable impacts on central fat gain, insulin sensitivity, and lipid profiles when therapy is started around menopause, which may contribute to lower long‑term cardiometabolic risk in appropriately selected women.
Neurological outcomes are more complicated. Some observational studies suggest neutral or slightly lower dementia risk with long-term estrogen-only therapy in younger older women, but combined estrogen–progestin regimens have been linked to a slight increase in Alzheimer’s disease with very long use. A large nationwide Danish case–control study found that women using systemic estrogen–progestin had a modestly increased rate of all-cause dementia and Alzheimer’s disease, even when treatment began at or before age 55 and especially with more than 12 years of use. Overall, major reviews and task forces advise against using MHT solely for dementia prevention; any potential brain benefit does not outweigh the uncertainty and possible harm.
Modern guidance from cardiovascular and menopause societies converges on a similar message: for healthy women with bothersome vasomotor symptoms, starting MHT before 60 and within 10 years of menopause is sensible, with an individualized risk assessment. Experts recommend carefully weighing personal and family health history (things like breast cancer, thrombosis, stroke, etc), rather than a one-size-fits-all recommendation.
Nevertheless, it's exciting to see a greater body of research forming consensus around this issue affecting 50% of the world's population.
Sources:
https://www.mayoclinic.org/diseases-conditions/menopause/in-depth/hormone-therapy/art-20046372
https://pubmed.ncbi.nlm.nih.gov/30484736
https://menopausenetwork.org/fda-hormone-therapy-update-menopause
https://pubmed.ncbi.nlm.nih.gov/29493798
https://www.jacc.org/doi/10.1016/j.jacadv.2025.101791
https://www.whi.org/md/whi-findings
https://www.bmj.com/content/381/bmj.p1404
