A large 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.
Study Details
The researchers divided women into three groups: those who started estrogen therapy during perimenopause and continued for at least ten years before menopause, those who began hormone therapy after menopause, and those who never used hormones. The study then tracked three major health outcomes over time: breast cancer, heart attack, and stroke.
The results showed that women who started therapy early had around 60% lower odds of developing all three conditions. In contrast, women who began estrogen therapy after menopause showed only minimal protective effects. The study also noted a slight increase in stroke risk, about 4.9% higher, for those who started after menopause compared to those who never used hormones.
Role of Estrogen
Estrogen plays a role beyond reproduction. It affects metabolic, cardiovascular, and cognitive health. When estrogen levels start to decline 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 and helps balance serotonin and dopamine, which can affect memory and focus. In bones and muscles, it helps preserve density and strength, which may reduce the risk of osteoporosis later in life.
When estrogen is introduced early, before these systems decline significantly, it may help preserve their function. Waiting until after menopause, when estrogen receptors have been without stimulation for years, may not deliver the same benefits and could pose more risk.
Implications for Women in Their 30s and 40s
For women starting to notice signs of hormonal transition, such as shorter cycles, sleep changes, mood shifts, or increased anxiety, the study suggests it may be time to talk with a healthcare provider. Perimenopause can begin 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 be better for long-term outcomes. However, hormone therapy is not the same for everyone. A qualified provider can personalize therapy based on symptoms, health history, and timing. Healthy lifestyle habits, including strength training, balanced nutrition, sleep, and stress management, also play a role in overall health.
The analysis adds to evidence that the timing of hormone therapy may be important. Starting estrogen during perimenopause may help protect the heart, brain, and bones for years to come.
