The Best Time To Start Hormone Therapy To Lower Disease Risk By 60%

If you’re in your 30s or 40s and starting to notice subtle changes—sleep that’s not quite as restorative, mood shifts, or cycles that suddenly feel unpredictable—you might be entering perimenopause, the hormonal transition leading up to menopause. 

And according to a massive new study presented at the 2025 Annual Meeting of The Menopause Society, this stage might be the most powerful window for protecting your long-term health with hormone therapy.

Why timing is everything

Researchers analyzed data from more than 120 million patient records and found that women who began estrogen therapy during perimenopause, and continued it for at least a decade, had about a 60% lower risk of developing breast cancer, heart attack, or stroke compared to those who started later or never used hormones at all.

In other words, timing matters.

For years, hormone therapy (HRT) has been viewed primarily as a tool for symptom relief–think hot flashes, night sweats, or mood swings. But this new analysis, presented at The Menopause Society’s 2025 Annual Meeting, adds to a growing body of evidence showing that starting estrogen therapy earlier may be key to unlocking its full long-term health benefits.

Inside the study

The researchers divided women into three groups:

Then they looked at three major outcomes, breast cancer, heart attack, and stroke, over time.

The results found that women who started therapy early (in perimenopause) had around 60% lower odds of developing all three conditions. In contrast, women who began estrogen therapy after menopause showed only minimal protective effects, and, interestingly, a slight increase in stroke risk (about 4.9% higher) compared to those who never used hormones.

Why earlier estrogen may protect your body (& brain)

Estrogen is far more than a reproductive hormone; it plays a critical role in metabolic, cardiovascular, and cognitive health. When estrogen levels start to fluctuate and decline in perimenopause, it affects nearly every system in the body.

Here’s how estrogen works behind the scenes:

When estrogen is introduced early, before these systems start to significantly decline, it can help preserve their function. But if you wait until after menopause, when estrogen receptors have been deprived of stimulation for years, hormone therapy may not deliver the same benefits (and, in some cases, could pose more risk).

What this means if you’re in your 30s or 40s

If you’re starting to experience signs of hormonal transition, like shorter cycles, sleep changes, mood fluctuations, or increased anxiety, it may be time to start a conversation with your healthcare provider now, not years down the line.

While hormone therapy isn’t one-size-fits-all, this new research reinforces that earlier is often better when it comes to optimizing long-term outcomes.

Here’s what to keep in mind:

Check out your peri/menopause+ guide for more expert-backed insights on treatment options, timing, and how to build a personalized plan that supports your long-term health.

The takeaway

This large-scale analysis adds to a growing body of evidence that when you start hormone therapy could make all the difference. Starting estrogen during perimenopause may not only help you feel more like yourself now, but also protect your heart, brain, and bones for decades to come.