Hormone therapy was once linked to dementia. A huge study found it might lower risk — if you start early enough.

A growing body of evidence suggests hormone therapy can protect the aging brain, if it's timed right.

Fiordaliso/Getty Images Hormone therapy may protect a woman's aging brain, but timing is critical.

Experts agree the "window of opportunity" for HRT is typically in the late 40s or early 50s.

"Early intervention promotes and sustains brain health," neuroscientist Roberta Brinton said.

Get in there early.

That seems to be the growing consensus around hormone replacement therapy (HRT) for women.

New study data suggests that middle-aged women could use these treatments to protect their brains, contradicting old concerns about a potential dementia risk.

There is a caveat to this good news: You probably have to adhere to what researchers are calling the golden "window of opportunity" before the brain hardens and ages too much.

Start boosting estrogen levels too late, and you may be doing more harm than good for your brain health , a growing body of research suggests.

"Early intervention promotes and sustains brain health, and postmenopausal intervention does not," neuroscientist Roberta Brinton, the director of the Center for Innovation in Brain Science at the University of Arizona, told Business Insider.

Slowly, but surely, old stigma and fear about HRT are being replaced by data-driven optimism that these cheap, widely available hormone treatments may be longevity-boosting drugs — especially for the heart, for the brain, and for the bones — but only when used in the right way, at the right time.

"When you take all these data, they substantially point in one direction," Dr.

Howard Hodis, a professor of medicine at the University of Southern California who's been studying the effects of hormone therapy on postmenopausal women for over three decades, said.

"That is, early: good; late: maybe no effect, and maybe harmful." Old fears about hormone therapy and dementia may not apply to women under 60 Hormone therapy can be administered through pills, patches, injections, or topical formulations like lotion or gel.