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CLEVELAND, Ohio — A new Case Western Reserve University study suggests that pre-menopausal women who used estrogen prior to menopause showed no significantly higher rates of breast cancer, heart attack and stroke compared to women who started estrogen after menopause or did not use it at all. These findings highlight the potential benefit of earlier initiation of estrogen therapy during perimenopause for minimizing risk and optimizing long-term health outcomes, university researchers said. The study was the largest-ever analysis of hormone replacement therapy using real-world patient data, the university said. Study results were recently presented at the 2025 annual meeting of The Menopause Society in Orlando. Estrogen therapy is effective and generally safe for managing bothersome menopause symptoms. However, there is a lack of data regarding the impact of initiating hormone therapy in perimenopause in terms of longer-term health outcomes, researchers said. Perimenopause is the transitional period before the final menstrual period. During these years, estrogen levels fluctuate and decline, and women begin experiencing menopause symptoms, researchers said. Case Western Reserve University scientists analyzed data from more than 120 million patient records. They looked for rates of breast cancer, heart attack and stroke associated with estrogen therapy when started during perimenopause, after menopause or not at all, the university said. “There has long been a debate about if and when estrogen therapy should begin, so hopefully the use of large-scale electronic health record data will help resolve that question,” said Ify Chidi, pre-med student and lead author in the Department of Population and Quantitative Health Sciences at Case Western Reserve University. Chidi’s mentor and professor -- Dr. Rachel Pope, Menopause Society Certified Practitioner at University Hospitals -- agrees. “We know that the safest time to start hormone therapy is within the first 10 years of menopause, but we wanted to know if it was also safe to start hormones prior to that when many women begin noticing symptoms—that is, during perimenopause,” Pope said. “Hopefully, these results start a larger conversation about prevention in women’s health and will incite more research.” For more information about menopause and healthy aging, visit menopause.org.
