Starting Estrogen in Perimenopause Cut Breast Cancer, Heart Attack, and Stroke by 60% — 120M-Record EHR Analysis
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Starting Estrogen in Perimenopause Cut Breast Cancer, Heart Attack, and Stroke by 60% — 120M-Record EHR Analysis

By Helena · · The Menopause Society 2025 Annual Meeting
KO | EN

Women who started estrogen therapy in perimenopause and used it for at least 10 years before menopause had roughly 60% lower odds of breast cancer, heart attack, and stroke compared with women who started later or never used hormones, according to a retrospective analysis of more than 120 million electronic health records. Ify Chidi of Case Western Reserve University School of Medicine presented the work as a poster at The Menopause Society 2025 Annual Meeting (October 21–25).

The poster, titled “The Timing of Estrogen Therapy: Perimenopausal Benefits and Postmenopausal Risks,” reopens a decades-long debate about when hormone therapy should begin. “There has long been a debate about if and when estrogen therapy should begin,” Chidi said. “Large-scale electronic health record data may help resolve that question.”

What’s new — timing changes everything

Living in WHI’s shadow:

  • The 2002 Women’s Health Initiative (WHI) tied hormone therapy to higher breast cancer and cardiovascular risk, and prescriptions collapsed
  • But WHI’s average participant was about 63 — women who started long after menopause
  • Re-analyses since have shown the risk profile is different for women who start within 10 years of menopause or before age 60

Chidi’s analysis:

  • 120+ million electronic health records
  • Comparison: started in perimenopause and used for 10+ years vs. started after menopause vs. never used
  • Result: ~60% lower odds of breast cancer, heart attack, and stroke in the early-start group

Reinforcing the “window of opportunity” hypothesis

The hypothesis:

  • A ~5–10 year window straddling menopause = the “opportunity window”
  • Hormone therapy started inside this window protects vasculature and brain
  • Starting more than 10 years after menopause runs into atherosclerosis and cognitive changes already in motion — harder to reverse
  • Late starts may carry more risk than benefit

Where this evidence sits:

  • Supports earlier RCTs (KEEPS, ELITE)
  • But this is a retrospective EHR analysis, not randomized
  • The 60% figure likely reflects an odds ratio, not absolute risk reduction — read the full presentation when available

What perimenopause actually is

Definition:

  • The 2–10 year transition before the final menstrual period (which itself is defined retrospectively as 12 months without bleeding)
  • Mid-40s to early-50s on average
  • The phase of greatest hormonal volatility

Symptoms:

  • Irregular cycles
  • Hot flashes and night sweats
  • Sleep disruption and mood shifts
  • Brain fog and concentration changes
  • Vaginal dryness, changes in libido

Diagnostic difficulty:

  • Hormone levels swing too widely for a single blood test to confirm
  • Diagnosis is clinical — symptoms, age, cycle pattern
  • The absence of a clean biomarker is part of why this kind of EHR study matters

Practical context for Asian and Korean women

Lower baseline prescribing:

  • Hormone therapy use in Korean menopausal women is ~5–10% (vs. 20–30% in many Western settings)
  • The post-WHI prescribing chill remains heavy
  • Traditional and natural alternatives are heavily preferred

What this data implies:

  • Late-start patterns common in Korea may forgo benefit that an earlier conversation could capture
  • When perimenopausal symptoms begin, gynecology and endocrinology evaluations should not be deferred
  • Family history (breast cancer, thrombosis) and individual risk factors remain decisive

Limits — this doesn’t apply to everyone

Study limits:

  • Retrospective EHR, not randomized
  • Women who pursued perimenopausal hormone therapy likely had better healthcare access and engagement (confounding)
  • “10 years of use” doesn’t guarantee a 60% personal risk reduction — individual variation is large

Where hormone therapy is contraindicated:

  • Personal history of breast cancer
  • Personal history of endometrial cancer
  • Prior venous thromboembolism or pulmonary embolism
  • Active liver disease
  • Known or suspected pregnancy

Alternatives:

  • Non-hormonal medical: gabapentin, SSRIs/SNRIs (for hot flashes)
  • Behavioral: CBT, exercise, sleep hygiene
  • Dietary: soy isoflavones (modest effect, generally safe)

The behavioral angle — “WHI trauma” as cognitive distortion

For 20+ years, many women and clinicians have carried a simplified “hormone therapy = breast cancer” framing rooted in early WHI headlines. This data argues that the simplification is expensive. Risk is not zero, but the start-timing, patient profile, and duration fundamentally change the risk-benefit balance. Decisions belong inside a full conversation with gynecology and endocrinology — and “avoid by default” is not the rational default the new evidence supports.

Tetrapod’s editorial position

Don’t defer hormone evaluation when perimenopausal symptoms start. After taking family and personal risk seriously, hormone therapy belongs on the table as a real option to weigh with a physician — not a category to dismiss reflexively. Supplements and diet sit on top of medical decisions, not in place of them.

Source: The Menopause Society 2025 Annual Meeting