A new study presented at the 2025 Annual Meeting of The Menopause Society suggests that starting hormone therapy during perimenopause may offer the greatest long-term health benefits.
Researchers analyzed data from more than 120 million patient records. They found that women who began estrogen therapy during perimenopause and continued it for at least ten years had about a 60% lower risk of developing breast cancer, heart attack, or stroke. This was compared to women who started hormone therapy later or never used it.
For many years, hormone therapy has been used mainly to relieve symptoms such as hot flashes, night sweats, and mood swings. This new analysis adds to evidence that starting estrogen therapy earlier may be key to gaining its full health benefits.
The study divided women into three groups. One group started estrogen therapy during perimenopause and continued for at least ten years before menopause. Another group began hormone therapy after menopause. The third group never used hormones. The researchers then tracked the occurrence of breast cancer, heart attack, and stroke over time.
Women who started therapy early had about 60% lower odds of developing all three conditions. Women who started estrogen therapy after menopause showed only small protective effects. This group also had a slight increase in stroke risk, about 4.9% higher, compared to those who never used hormones.
Estrogen plays a role beyond reproduction. It affects metabolic, cardiovascular, and cognitive health. When estrogen levels begin to change and drop during perimenopause, it impacts many body systems. In the heart, estrogen helps keep blood vessels flexible and supports healthy cholesterol levels. In the brain, it promotes neuroplasticity, supports serotonin and dopamine balance, and aids memory and focus. In bones and muscles, it helps preserve density and strength, which can lower the risk of osteoporosis and frailty later in life.
Introducing estrogen early, before these systems decline significantly, may help preserve their function. Waiting until after menopause, when estrogen receptors have been without stimulation for years, may not provide the same benefits and could pose more risk.
For women in their 30s or 40s who notice signs of hormonal transition, such as shorter cycles, sleep changes, mood shifts, or increased anxiety, the study suggests talking to a healthcare provider now. Perimenopause can start as early as the mid-to-late 30s. Tracking cycles, symptoms, and energy levels can help identify changes.
The study reinforces that earlier use of hormone therapy may lead to better long-term outcomes. The research adds to a growing body of evidence that the timing of hormone therapy could make a difference in protecting heart, brain, and bone health for years to come.
